The Government has apologised after admitting it underestimated the number of immigrant workers in Britain by almost a quarter.

Peter Hain, the Work and Pensions Secretary
Peter Hain admitted that 300,000 foreign workers were left out of official statistics

Peter Hain, the Work and Pensions Secretary, conceded that 300,000 foreign citizens working in Britain had been left out of official statistics.

Some 1.1 million people from abroad have taken jobs in Britain since 1997, the Government said, meaning immigrants have taken 40.7 per cent of the 2.7 million new jobs created over the period..

“Of course it is bad that these figures are wrong and ministers have apologised for that, I am sorry about that,” Home Secretary Jacqui Smith told BBC Breakfast.

The admission comes as MPs prepare to leave Westminster tomorrow for a break before the Queen’s Speech next week.

The DWP insisted ministers had used the earlier estimate “in good faith” and attributed the rise to more detailed analysis of labour force data.

“I apologise for having to make this revision. I am sure you will understand these calculations are not straightforward,” Mr Hain wrote in a letter to the Speaker and the opposition parties.

Liam Byrne, the immigration minister, admitted that officials still do not know where the foreign workers come from.

He told Channel 4 News: “It’s one of the reasons why we are introducing systems to count people in and out.”

Shadow immigration minister Damian Green said the Government’s figures on immigration were “as all over the place as its policy”.

He said: “300,000 is quite a significant figure of people in this country who the Government don’t know about. For all the introduction of a points system and so on, the Government won’t take the basic important step of putting an explicit annual limit on the number of people coming in to work from outside the EU.

Sir Andrew Green, chairman of Migrationwatch, which campaigns against mass immigration said that 300,000 is equivalent to “the entire city of Coventry”.

It is impossible to have a sensible discussion on immigration if the government keeps getting its figures hopelessly wrong,” he said.

Mr Byrne had earlier confirmed that “transitional” restrictions on Bulgarians and Romanians coming to Britain to work will remain in place for another year.

The number was capped at 20,000 when their countries joined the EU in January.

The row followed a speech by David Cameron in which he promised that immigration would be “significantly” lower under a Tory government.

In his first major speech on immigration since becoming Tory leader in 2005, Mr Cameron said Gordon Brown had failed to come up with a coherent policy on changes that will swell the population to 70 million in 25 years.

In a speech to the Policy Exchange think-tank in London, Mr Cameron confirmed plans to establish a Border Police Force with powers to track down and remove illegal migrants and to impose “transitional controls” on the entry of citizens from any new European Union members.

He outlined restrictions for arranged marriages, such as raising the minimum age for would-be spouses to 21. Mr Cameron had previously avoided talking about immigration for fear of being branded an extremist by Labour.

But having built a lead in the polls, Tories now feel the time is right to try to reclaim the issue from Labour.