Britain's foreign-born population has risen above eight million for the first time, University of Oxford experts said today.

The independent Migration Observatory said official figures set to be released on Thursday would almost certainly confirm the landmark figure had been surpassed.

It also warned that net migration into Britain may have hit a record high last year, despite David Cameron's set-piece election pledge to slash the number of foreign workers moving to Britain.

Britain's foreign-born population is set to officially rise above eight million for the first time when official figures are published on Thursday, University of Oxford experts said today

The number of people living in the UK who were born in the EU has rocketed - but is still far below those born elsewhere in the world

The last set of figures published by the Office for National Statistics showed annual net migration in to the UK had surged to 318,000.

This was just 2,000 below the 320,000 record high set in 2005 after Tony Blair opened the borders to eight eastern European countries the previous year.

Ahead of the 2010 general election Mr Cameron pledged to reduce net migration 'from the hundreds of thousands to then tens of thousands'.

Despite coming nowhere near meeting the pledge, the Prime Minister reiterated his 'goal' to slash net migration at the last election.

Britain has a higher proportion of citizens born abroad than either France or Germany - but is still some way short of Austria, Ireland, Sweden, Belgium or Spain

Ahead of the 2010 general election David Cameron pledged to reduce net migration 'from the hundreds of thousands to then tens of thousands'

However, according to a briefing published by the Migration Observatory this morning, the true number of foreign-born citizens in Britain is likely to be higher than official figures suggest.

It said the number of people living in the UK who were born abroad has increased each year for a decade and is on track to officially exceed 8 million for the first time.

But it said the 8 million threshold 'is actually likely to have been crossed more than a year ago' because there is a lag in the ONS's figures.

Overall, the share of the British population born abroad is broadly in line with other countries in Europe.

In 2014, six countries had larger foreign-born shares of the population than Britain - including Austria, Ireland and Sweden. Nine other countries had smaller shares, including Italy, Portugal and Finland.

Immigration minister James Brokenshire unveiled a fresh crackdown on illegal immigration today

Ahead of the official migration figures set to be published on Thursday, ministers today unveiled a fresh illegal working.

Immigration minister James Brokenshire announced that under new rules illegal immigrants will face up to six months in prison for working in the UK.

The new crackdown will also see late-night takeaways and off-licences facing closure if they are caught employing foreigners who have no legal right to be in the country.

Details of the legislation have been revealed after the Government faced criticism for its handling of the Calais crisis.

Immigration Minister James Brokenshire said: 'Anyone who thinks the UK is a soft touch should be in no doubt - if you are here illegally, we will take action to stop you from working, renting a flat, opening a bank account or driving a car.

'As a one nation government we will continue to crack down on abuse and build an immigration system that works in the best interests of the British people and those who play by the rules.

'Illegal workers will face the prospect of a prison term and rogue employers could have their businesses closed, have their licences removed, or face prosecution if they continue to flout the law.'

Earlier in the year the Government announced that a new offence of illegal working will allow wages to be seized as proceeds of crime.

Now the Home Office has disclosed that anyone convicted under the powers in England and Wales could face a sentence of up to six months and an unlimited fine. Rogue businesses are also being targeted.

Under the new regime, any pub, off-licence or late-night takeaway that fails to comply with immigration laws or employs illegal workers could be stripped of their licence to operate. Officials are also considering whether this power should be extended to cover minicab drivers and operators.

The law on cases for deliberately employing illegal workers will be changed to pave the way for more prosecutions.

A lorry passes through UK Border Control at the Eurotunnel site in Calais amid growing pressure on immigration officers to stop migrants breaking into Britain

Up to 5,000 migrants are thought to be camped around Calais trying to make their way into the UK on lorries

Precise details of the reform have not been given but it is expected to mean lower requirements on the evidence needed to prove the offence by forcing accused businesses to show they have carried out all relevant checks before employing an individual.

The maximum sentence for those found guilty will be raised from two to five years in addition to heavy fines which are already levied against culprits.

Employers who continue to flout the law and evade sanctions could see their business closed for up to 48 hours while they prove right-to-work checks have been conducted on staff.

Courts would then place the worst offenders under 'special measures' such as forcing them to remain shut or carrying out ongoing compliance checks.

Alp Mehmet, of Migration Watch UK, which campaigns for tighter immigration restrictions, said: 'This is not just about not being seen as a soft touch.

'More important is for the message to go out that if you are here illegally and caught working, you and your employer will end up in court.