The moment Poland joined the EU, its citizens rushed for the exits. Five thousand doctors alone have left since 2004. But what's so bad about the old country, or so great about destinations like Britain? Helen Pidd and Luke Harding report from beautiful, cultured - but unloved - Wroclaw

At bay number four in Wroclaw's bus station, a group of young Poles are standing around in the afternoon sunshine. Among them is Michal Wardas, a 24-year-old university student. He is off to spend the next two months working as a waiter on the Isle of Wight. "I like Britain. The people are friendly. I've been four times in the past two years," Wardas says, dumping his rucksack on the 51-seater Globus coach, and climbing on board for the 20-hour journey to London.

The trip will take him through the drab motorway landscape of central Europe - down Germany's autobahns, through Holland and the town of Eindhoven, and into Britain via Calais and the Channel tunnel. There will be lots of free coffee, and videos of Polish comedies and Mr Bean - not a bad introduction to life in Britain, perhaps, for Poles not fluent in English. Wardas's mum, Teresa, has come to wave him off. "I'm very sad he's leaving," she says. "When I grew up you couldn't visit the west. The only place we could go was the Soviet Union. But this is a different generation."

What makes this scene in Wroclaw, in south-west Poland, unusual is the epic scale of the exodus. On quiet days six buses leave for "Anglia", the Polish word for England; when it's busy, it is 15. The buses are all full; you have to book. With Ryanair flying twice a day between Wroclaw and Stansted as well, a quick back-of-an-envelope calculation reveals that around 1,000 Wroclavians a day are heading to London, Liverpool, Manchester, Stoke-on-Trent and other UK destinations. Nobody knows how many Poles go back home. But given that the Ryanair fare from Wroclaw to London often costs three times as much as flying in the other direction, it is clear that most of the traffic is heading one way.

Wardas is part of the biggest wave of emigration into Britain for three centuries. Official statistics suggest that 228,000 Poles have registered to live and work in Britain since Poland joined the EU in May 2004. Other estimates suggest the real figure is between 350,000 and 500,000, while last week the respected Polish news magazine Polityka estimated that one million Poles have moved to the UK. Some 83% of them are under 34. This benign invasion of eager and biddable young Poles has, it is generally agreed, been marvellous for the British economy and anyone who had previously struggled to find a cheap plumber.

But what has the impact been on Poland, where 16.5% of inhabitants are unemployed and the average national wage is just £5,226 per year? Some two years on, there is a growing realisation that the "brain drain" now gripping eastern Europe's biggest country is nothing less than a national disaster. "In my neighbourhood near Warsaw some 25 businesses have closed down," noted Krystyna Iglicka, an expert on demography at Warsaw's Centre for International Relations, this week. "The boy who delivered my pizza has disappeared. My hairdresser has gone. The gardener who used to do my garden now works in Great Britain for a landscape architect. A friend of mine took him. My local garage has shut down. Everyone has moved to Britain or to Ireland."

In Wroclaw, Poland's fourth largest city with 675,000 inhabitants, officials are seriously worried. With its Gothic churches, baroque university and languid willow-lined canals, this historic town on the banks of the Odra river could hardly be more enticing. Germany is a few hours' drive away, the Czech Republic and Sudety mountains are nearby. Formerly ruled by the Austrians, Bohemians and the Germans - who left in 1945 - it is probably Poland's most European city. At night tipsy students stagger arm in arm down the restored medieval streets; swallows circle the cathedral's twin towers; you can even see the odd nun sending an SMS.

But the problem, as the city's ambitious mayor, Rafal Dutkiewicz, explains, is that much of Wroclaw's educated workforce has gone. "It's irritating that nobody has been talking about this issue," he says, speaking from his office overlooking the Rynek, Wroclaw's pretty cobbled market square. "I'm a big fan of a free Europe. I believe people should be allowed to make their own decisions. At the same time it's my job to try and create an alternative so that not everybody goes off to Britain."

The mayor is trying to persuade some of the thousands of Poles who have decamped to Britain to come back. The city has launched an advertising campaign in Polish papers in Britain under the slogan: "Wroc-loves you." It has set up an internet site for homesick Poles (www.terazwroclaw.pl) and taken out radio adverts on Polish radio stations such as Radio Orla in London. It is even sponsoring Polish cultural events - not folk choirs in national costume, but gigs at the 2,000-capacity London Astoria and other major venues. ("We didn't want to do anything too formal. We wanted to get across the message that Wroclaw was cool," says Pawel Romaszkan from Wroclaw's tourism office, who will be touring Britain in September and October, with the message: "Come home." And since 2001, Polityka has launched another scheme called Stay With Us, sponsored by some of Poland's biggest companies, to persuade the country's leading young academics to resist the lure of foreign shores. So far, about 100 rising stars have received around £4,200 to stay put.

Unfortunately, most Poles now in London consider the idea of going back to their homeland a non-starter. "Why on earth would I go back?" says 34-year-old Rafal Stanczak from Wroclaw, who has been driving vans in Britain for a year. "Here I get four times the wages I got in Wroclaw, and it is only twice as expensive to live."

But it's not just about the money. Ask almost any young Pole in Britain why they are here, and chances are they will say they fancied an adventure. Unlike previous generations, whose only chance to experience the west was on TV, this lot - just like their contemporaries the world over - are keen to travel. "We're living in a free Europe now and I want to see as much of it as possible," says one Pole in London, Jacek Rudnicki. "I love Wroclaw," says 28-year-old Jacek Zelaszkiewicz, who is standing in the city's biggest square, "but I want to see other cities; big places where I won't bump into an ex-girlfriend on every corner."

If Wroclaw is unable to tempt people back, there is little hope that the more depressed towns in the region - with their communist-era tower blocks and ageing population - can do any better. Instead, the dire consequences for Poland are becoming increasingly clear. There are labour shortages in several sectors of the Polish economy - in services, trade, the building industry and science. The most acute problem of all, however, is in medicine. Some 5,000 doctors have left Poland over the past two years. In Lower Silesia, where Wroclaw is located, a quarter of all anaesthetists have applied for the special certificate that allows them to work abroad; nationally the figure is 14% (see Agnieszka Walecka case study, p9). One hospital in the region recently suspended operations because all 10 anaesthetists walked out in protest at low pay. Poland's underfunded health service is also running out of nurses.

"The situation is drastic. There are too few anaesthetists," says Jerzy Wyszumirski, vice-president of Poland's anaesthetists' association. "Of course this affects patients. Doctors are over-tired, frustrated and in a hurry. We are now working 70 hours a week. In this situation there are bound to be mistakes." Has anyone died yet? "No. But to give you a hypothetical example, in an emergency we may now be able to treat only one patient instead of three."

In Poland, an anaesthetist earns as little as 1,200-1,400 zloty a month - £200. A top specialist might get 10,000 zloty - £1,600. Such salaries spectacularly fail to compare with the NHS, where anaesthetists earn £45,000-£110,000 a year, and have far greater opportunities for professional development.

Last year Wyszumirski wrote to Poland's health ministry, pointing out that "embarrassingly low wages" meant that all the best doctors were leaving the country. Last month the ministry wrote back. It said it was "monitoring" the situation and promised higher pay and more anaesthetists. Poland's eccentric rightwing coalition government - headed by president Lech Kaczynski and his prime minister twin brother Jaroslaw - appears not to have got to grips with the problem. But even if Poland does manage to train more doctors, it seems inevitable that many of them will end up in Bristol or Glasgow.

For the moment, then, the lure of higher wages in the UK is irresistible, not just for middle-class professionals but also for anyone with ambition, prepared to take a low-skilled job and improve their English. According to figures from the Home Office, at least two-thirds of Polish immigrants in Britain take society's lowest paid work. "In England I can earn five times as much as in Poland," says Lukasz Nowak, a 24-year-old student boarding the bus to Anglia. "I've never been in Britain before. But I'm going to stay with a friend. He's promised to find me a job. Apparently it's easy." Can he speak English? "Nie."

Those left behind find the exodus to Britain as irritating as it is understandable. "It's our educated young people who are leaving," complains Alicja Zubik, a partner in a successful estate agents in Wroclaw. "The only reason is money. The Polish taxpayer paid for their education in the first place." Her most promising young employee was economics graduate Kamila Smakulska. She set off for London a year ago, and is now working as a waitress.

Zubik admits Smakulska has been hard to replace. She points out that at crucial moments in Poland's history much of the country's population has cleared off. It happened when Russia, Austria and Prussia partitioned Poland in the 19th century, effacing it from the map; there was another wave of mass emigration in the early 20th century; then the catastrophe of the second world war, and communist rule. "Poland has been running to catch up. But we keep on falling into a hole. Our skilled people are always leaving," she says.

What would her message be to Smakulska and other young Poles in Britain? "I would say, 'Be happy'. Take the best examples and best practices from abroad. And then come back." But Smakulska doesn't feel guilty for leaving - in fact, every Pole we spoke to in London thought that EU membership was a good excuse to desert their country, albeit temporarily: the vast majority say their sojourn in the UK is not permanent.

The wave of migration to Britain since 2004 has brought some benefits. Last year Poles working outside their country sent home 22bn zloty - almost £4bn. Economists calculate the money accounted for 1.5% of Poland's economic growth last year, now running at 5%. The country's chronic unemployment rate is also shrinking: there are now 300,000 fewer jobseekers than last year, although this doesn't necessarily point to massive job creation, given the number of people who have left the country.

At the same time wages have gone up by 8%. For the first time Polish politicians have started discussing how to fill labour shortages in Poland itself, with calls for restrictions to be lifted so that Ukrainians and Belarussians can come and work. As Poles leave for Britain, workers from even lower-wage countries move to Poland - a sort of globalisation merry-go-round. And if the experience of previous migrations is anything to go by, many of the Poles in Britain will come back. Demographers identify two kinds of migrant - the "hamsters" who curl up and stay in their adopted country, and the "storks" who go abroad seasonally but eventually fly home.

"People are leaving," says Rafal Dutkiewicz. "But some will return. When they do, we want to present Wroclaw as a really nice city for them to live in."

Back at Wroclaw bus station, the latest coach to Anglia is pulling in. The coach's driver, Gienek, says he likes Britain but would never consider actually living there. "I've travelled all over Europe," he says. "I've been to Italy, France and Germany. I like Britain. But at the end of the day it's nothing special"

Pawel Glijerski

In Poland: a fruit juice salesman

In Britain: drives a forklift truck for Tesco

"If you can speak English, it's easy to get a job in the UK," says Glijerski, who since February has been in Milton Keynes working for Tesco's massive distribution centre. Everything was organised before he stepped on the plane. He spotted an advert in Gazeta Wyborska, Poland's bestselling newspaper, which said, "Work in Great Britain! Excellent rates of pay!" alongside a freephone number.

Glijerski called and, thanks to his language skills and forklift truck licence, soon had a job. Tesco organised everything, including shared accommodation at £60 per week - more, as Glijerski notes wryly, than the going rate in the area. Tesco's pay - just over £8 an hour - is good. A speculator with an excellent economics degree, Glijerski is planning for the future, and much of his wages are put aside to pay for two flats he bought off-plan in Wroclaw last year. "It's frustrating sometimes, having a good education and spending all day every day haring around in a warehouse," he says, "but this isn't a permanent thing." When he has earned enough, he's going to head back over to Wroclaw, move into one of his flats with his girlfriend and become a broker on the stock exchange.

He enjoys the job, and says he can understand why some of his colleagues speak badly of the Polish invasion. "I read in the news about Peugeot closing down its plant in Coventry, and other mass redundancies, so I can appreciate how people feel seeing how easy it is for foreigners to get jobs here." One man complained to Glijerski that it was unfair that he, as a Pole, had such a plum job while the British man's wife was unemployed. "He asked me how this could be the case. And because I have a masters in economics I was able to explain it to him."

Agnieszka Walecka, 36

In Poland: an anaesthetist

In Britain: an anaesthetist

In 2005, after almost 14 years of medical training as an anaesthetist, Walecka was earning 1,750 zloty (£300) a month working at the Lower Silesian Lung Diseases Hospital in Wroclaw. Despite being just one grade below consultant level, she had to take private work in the evenings to supplement her income, and lived with her mother in a semi-detached house in the city. It was not unusual for her to work 24 hours or more at a stretch - which, as she says with droll understatement, "isn't good for anyone, especially anaesthetists".

Last year, fed up with working round the clock and frustrated at the lack of training opportunities offered to doctors in Poland, she followed a colleague to Britain. Her first post was at a hospital in Swindon, and since April she has been working at the Charing Cross Hospital in London.

Here, her annual salary is around £45,000. She rents a two-bedroom flat in a desirable part of west London and is actively encouraged to take time to get her medical knowledge up to date. Back in Wroclaw, where an astonishing 25% of anaesthetists have applied for the special certificate that allows them to practise abroad, her hospital struggles on. A year ago there were eight anaesthetists, which wasn't nearly enough. Now, with Walecka and her colleague gone, there are six, with no hope of replacing the deserters. Dr Jerzy Wyszumirski, vice-president of Poland's anaesthetists' association, and a former colleague of Walecka, is clearly worried: "We have a real problem. There are not enough of us left. Operations are being cancelled or postponed. The waiting lists are getting longer. We are trying to find new people. But it's proving very difficult."

But Walecka doesn't feel guilty. "I want to help them," she says. "I want to encourage them to come to Britain, where they have the opportunity to really progress in their career. Even if they come for an unpaid placement, it will be worth it for them. It won't even cost them anything; they can stay in my flat."

Piotr Dobroniak, 29

In Poland: a well-paid manager

In Britain: a labourer

Piotr Dobroniak had a good job back in Wroclaw. After working for seven years at a big cash-and-carry chain in Dlugoleka, 10km from Wroclaw, he had risen through the ranks to become a manager, a very well-regarded position in Poland. By 2005 he had around 40 people working under him and took home 7,000 zloty (almost £1,200) a month, far above the national average of £435.

He was happy and well-off, but bored and still, aged 28, having his style cramped by living at home with his mother and grandmother. One day, he and a friend were having the usual conversation about what a dead-end place Poland was. This time, they decided to do something about it. Within two weeks Dobroniak was on a bus to London. Twenty hours later, he arrived at Victoria and practised saying "Hello! I'm looking for a job" until he no longer stumbled over the words.

Getting a job in Britain as an immigrant is one big Catch-22. For above-board positions, you can't be employed without a British bank account and a National Insurance number; the twist is that you can't get an NI number without backing from a potential employer. Then there was the added problem of his nationality. One of his first jobs was as a builder at the new Wembley stadium. There was a lot of tension between the British and foreign workers. "One day, one of the English guys said, 'It's too bad that Hitler didn't kick your asses properly'," he remembers.

Dobroniak now works as a labourer for a stonemasonry company, earning £50 a day before tax. It may be less than he earned back home, but that, he says, is not the point. "Here I feel free." Back in Wroclaw, one of his former colleagues, Michal Grabowski, says the firm has been unable to replace Dobroniak with a worker of the same calibre. "They're just getting weaker and weaker," he says. Grabowski has just enrolled on an English course and hopes to try his luck in Britain within a year.

Happy in London, Dobroniak says he may never go back. Things are looking up. He has just had an interview for a job as a manager with Lidl supermarket. He was worried he wouldn't stand a chance because of his shaky English, but the interviewer wasn't perturbed. "After all," she said, "almost all of the workers are Polish anyway."

Rafal Stanczak, 34

In Poland: a rep for a pharmaceutical company

In Britain: a van driver

It was the corruption that got to Stanczak in the end. "I just woke up one day last year and knew that I had to get out," he says, in the garden of the three-bedroom house in Seven Sisters, London, that he shares with five other Poles. "Poland is sick. Corruption, affairs, scandals ... I had had enough. I had no wife, no kids and was going nowhere." So he left. Just like that. And he's not regretting it.

"Here there is less nepotism. It's more of a meritocracy. You get the job if you've got the skills, not if you know the right people." But more important than work, he says, is the freedom afforded by life in Britain. "Here I have carte blanche to do whatever I want. After one week's work here, I could buy plane tickets to go to Barcelona. I can hop on the tube and go and see concerts. I love it."

Back in Wroclaw, his friend Jacek Zelaszkiewicz says he's not surprised that Stanczak upped sticks and left. "No one in Poland can understand that it's OK to be 34 and to have not started a family yet," he says. Though Zelaszkiewicz has his own business running a record shop in Wroclaw, he too is planning to leave. "I have to get the money together to pay my mortgage," he says.

Kamila Smakulska, 27

In Poland: an estate agent

In Britain: a waitress

It was a combination of love and adventure that brought Kamila Smakulska to Britain a year ago. Her long-term boyfriend, Krysztof, was already in London, and Smakulska had itchy feet. "I just wanted to change something in my life," she says. "I had a good job, working at an estate agents in Wroclaw, and I could live quite well, but even on 2,000 zloty a month (£340) I couldn't afford my own flat and wanted to see something new."

She now lives with Krysztof in North Acton, a very Polish area of London. Back home, that wouldn't have been possible unless they were married. "It's a Catholic and cultural thing," she shrugs. She now works as a waitress at Westminster City Hall, earning £200 a week after tax, and is taking English lessons three evenings a week. She was only planning to stay for a few months, but is now thinking about doing a Masters. She misses the main square in Wroclaw, and the Japanese gardens too, but says the only thing that would get her back home right now would be family problems. "The mayor's campaign [to lure Poles back from Britain] will never work," she says. "I know so many people in Wroclaw who can't find a job."