Mass immigration has led to a fall in the number of Britons with jobs, according to official figures.

Since 2004, when citizens of eight central and eastern European countries were given the right to work in Britain, the number of UK-born people working here has fallen by 500,000, from 24.4 million to 23.9 million, the Office for National Statistics (ONS) revealed Over the period, the number of migrants in work, including people born abroad but now naturalised as British citizens, rose by 1.1 million to 3.3 million. They now make up one in eight of the workforce, it said.

The figures provide the strongest evidence yet that Britons have lost their jobs to immigrants, a leading expert on immigration said.

The Daily Telegraph quoted Robert Rowthorn, a Cambridge University professor who uncovered the findings, as saying, ''It seems hard to deny that immigration from the new EU member states has had a negative impact on the employment of UK natives.'' The ONS figures showed that between 2001 and 2007 the number of UK-born British nationals in employment fell by 495,000.

Prof Rowthorn said the most likely victims were British-born school-leavers who had never had a job, having failed to find the kind of casual work they might have walked into a few years ago.

''We are looking at the most vulnerable, least skilled and in some ways least motivated members of the local workforce. The problem that eastern European migrants pose is that they are good workers,'' he added.