Criminal gangs are selling genuine British passports for less than £500 to migrants in Europe, it can be revealed today.

The price of a stolen passport has dropped dramatically from £2,000 a year ago, after more than 20,000 identity documents flooded on to the black market.

It raises fears that Islamic State fanatics intent on committing terror attacks in the UK are finding it easier than ever to reach our shores.

Criminal gangs are selling genuine British passports for less than £500 to migrants in Europe, it can be revealed today. A man is caught on camera offering an illegal passport in Athens

A senior police chief described the illicit trade as ‘one of the fastest growing problems’ in Europe.

Rob Wainwright, the director of Europol, raised deep concerns that current border controls are unable to cope with ‘sophisticated counterfeit criminal syndicates’.

He said terrorists were ‘exploiting’ the surge of migrants into Europe to move about undetected.

Meanwhile, two current UK Border Force officials warned that thousands of black market passports may have been used to enter Britain in the past year.

The whistleblowers expressed grave concerns about our national security and suggested that ‘border security is non-existent’.

And the Border Force admitted it had seized more than 6,500 illegal documents at passport control in the past three years. That figure is double the 3,000 passports seized during the three previous years.

The price of a stolen passport has dropped dramatically from £2,000 a year ago, after more than 20,000 identity documents flooded on to the black market

The ease at which it is possible to obtain British passports on the black market in Europe was laid bare by an undercover investigator in Athens.

The man, known only as Hashmet to protect his identity, was able to obtain a phone number of an illegal passport seller within minutes of entering Victoria Square, where migrants congregate in the city.

Hashmet, who was working on behalf of ITV’s Tonight programme, then met another member of the criminal gang who offered him a selection of British passports.

For 500 euros – about £460 – he was offered a British passport, thought to have been stolen, of a man who has similar features to him.

The smuggler suggested that Hashmet would have to alter his appearance and suggested he dyed his hair blond to look like the person featured on one of the passports he was trying to sell.

He also told the investigator that he could replace the photo in one of the British passports for a picture of him for an extra 300 euros, which is £276.

This deal included advice on which airports in the UK have the lowest security and other tips on fooling British immigration officials.

Hashmet was advised that migrants have a better chance of sneaking into Britain using a ‘lookalike’ passport, rather than a doctored one.

It raises fears that Islamic State fanatics intent on committing terror attacks in the UK are finding it easier than ever to reach our shores

After exposing the illegal trade, Hashmet said: ‘The business of buying passports is quite common here. The smugglers don’t question your motives for getting into any country. It doesn’t matter to them as long as you have the money.

‘Smugglers say there is a high rate of success, but I’ve also talked to immigrants and they tell me, “my cousin, my friend or my flatmate made it” [into the UK], so there are some success stories.’

Concerns over the supply of fake documents were laid bare by the EU’s border agency earlier this year.

It said there were 11,000 migrants living in Europe with forged documents – a figure than has almost doubled in six months.

Mr Wainwright told Tonight: ‘I think it is one of the fastest growing criminal problems we have in Europe. Over 20,000 of them we know are circulating in the EU and we haven’t seen these numbers before so it’s quickly becoming something that’s really supporting a number of criminal problems and in an expanding way across Europe.

‘I think the migrant crisis was definitely a spur. In 2015 we had five times as many irregular migrants coming through the external border of the European Union compared to the year before. That created this whole new demand for a criminal industry that quickly established over the following months.

‘I’m afraid the reality is we are facing highly challenging, volatile security threats – especially in the field of terrorism which are really stretching the capability of our security community across Europe.’

The Europol chief added: ‘I’m concerned about just how sophisticated these counterfeit criminal syndicates have become and whether or not our border control systems are up to par in meeting this renewed threat.’

Two current Border Force employees, who agreed to speak on the condition of anonymity, told how the agency was struggling to catch all of those on illegal passports.

One said: ‘We’re increasingly relying on a short term, poorly trained seasonal workforce because we don’t have enough substantive members of staff.

‘They’re brought in with no knowledge and no experience and they’re going to be given a few days training here and there. They’re not sufficiently trained and not sufficiently knowledgeable to be conducting an adequate immigration control and I would have concerns about national security as a result.’

The second added: ‘We are also just operating with officers who – through no fault of their own – just aren’t equipped to do the job so the pressure falls on the more experienced staff. We’re making mistakes left right and centre.’

In the latest Home Office staff survey fewer than one in five Border Force staff said they believe the agency to be well organised.

Emma Moore, Border Force’s chief operating officer, defended her agency’s immigration checks.

‘All passengers have 100 per cent checks at on their arrival into the UK,’ she said. ‘That never changes and that doesn’t change regardless of demand.

‘Our primary purpose is to maintain security at the border, although we will manage our queues as much as we can, everybody does need to be checked and sometimes that takes time. The issue of staffing is a perennial one.

‘In the last three years we have seized over 6,500 forged documents at passport control.’