Political parties have been warned not to inflame racial tensions in the general election by the chairman of the Commission for Racial Equality.

The atmosphere in the campaign is sour, fractious and brittle, Trevor Phillips tells the Times.

He said: "I am probably the most worried person in the country at the moment."

The commission has received reports of racist violence, intimidation and "mob rule" in the past month, he added.

His comments came as a prospective Conservative candidate admitted doctoring photographs in his campaign literature to emphasise his party's tough stance on immigration.

Ed Matts, the Tory candidate in the marginal seat of Dorset South, has a photo showing him and former shadow home secretary Ann Widdecombe holding placards bearing a tough message about immigration.

But the original picture, published in the Dorset Echo last month, shows him holding a photograph of Malawian asylum-seeker Verah Kachepa and her four children, protesting against their deportation.

Widdecombe's placard says: "Let them stay."

Prospective Labour candidate Jim Knight, who has a 153 majority over the Tories, said: "It's clearly dishonest to remove the words saying 'let them stay' just because the placard contradicted Tory immigration policy."

Meanwhile Michael Howard has claimed a temporary admission policy is increasing the terror risk of the government's immigration policy.