Immigration was at the centre of the election campaign today as it emerged that virtually every extra job created under Labour has gone to a foreign worker.

Figures suggested an extraordinary 98.5 per cent of 1.67million new posts were taken by immigrants.

The Tories seized on the revelation as evidence that the Government has totally failed to deliver its pledge of 'British jobs for British workers'.

As Gordon Brown tried to fight on the economy and cleaning up politics, he was confronted in the Commons about how British people of working age have lost out.

 Shadow immigration minister Damian Green revealed unpublished figures showing there are almost 730,000 fewer British-born workers in the private sector than in 1997.

Last night Mr Green said the Tories would reduce net migration to tens of thousands a year from the peaks of 200,000 under Labour by enforcing an annual cap.

Mr Brown rejected the idea of an immigration quota, which he said would do 'great damage to British business'.

But Mr Green said the official figures were 'the final proof that Gordon Brown was misleading the public when he promised British jobs for British workers'. He added: 'Instead he has presided over boom and bust and left British workers in a worse position than when he took office 13 years ago. 'British workers have been betrayed. A Conservative government would introduce a genuine limit which would help us properly control immigration.

Shadow immigration minister Damian Green revealed the figures yesterday  'We would reduce net immigration to the levels of the 1980s and 90s - tens of thousands a year, not the hundreds of thousands we have seen under Labour.'

The ONS figures show the total number of people in work in both the private and the public sector has risen from around 25.7million in 1997 to 27.4million at the end of last year, an increase of 1.67million.

But the number of workers born abroad has increased dramatically by 1.64million, from 1.9million to 3.5million. There were 23.8million British-born workers in employment at the end of last year, just 25,000 more than when Labour came to power. In the private sector, the number of British workers has actually fallen.

The number of posts for people of working age has increased since 1997 by over 500,000, to 20.5million. But the number of British-born workers in the private sector has slumped by 726,000, from 18.4million to 17.7million.  The figures exclude people working beyond pension age, which critics say the Government includes as 'new jobs' in its assessments.

Last year, the Organisation for Economic Co-operation and Development said that, over ten years, only Luxembourg had seen more of its new jobs taken by migrants. The latest totals do not include the hundreds of thousands of migrants employed in the 'black economy'.

Sir Andrew Green, of the Migrationwatch pressure group, said: 'The government's economic case for mass immigration is finally blown out of the water.'

A Labour Party spokesman said: 'Net inward migration has fallen and Labour has set out how we will use the points-based system to ensure that, as growth returns, our priority is to see rising levels of skills, wages and employment, not rising immigration. 'But we reject a Tory quota which is arbitrary and misleading - not covering most of those who apply to come to Britain - and bad for business and growth.

Mr Brown attempted to defend the figures in the House of Commons 'Under the points-based system the door is currently closed to unskilled workers from outside the EU, and the rules are being tightened on students working part-time. Skilled jobs must be advertised in Jobcentre Plus before being opened to migrant workers.

'Unemployment is around half a million lower than people anticipated last year, as thousands of British workers benefit from the help and support we offer. 'With more than 480,000 vacancies right now we are making sure no one gets left behind.'