'We don't even know how many migrants there are in Britain', says minister

Sadiq Khan, a government whip and the MP for Tooting, said nobody had "confidence" in the Government's own statistics on the levels of lawful and unlawful migrants.

Mr Khan said the Government also needed to recognise "the real problems" faced by local authorities because central funding allocations did not always take into account the increased pressures on services caused by immigration.

"There's no real confidence in official figures," he told a fringe meeting organised by the Foreign Policy Exchange.

His comments come amid a growing row between local authorities and the Government over the way the Office Of National Statistics records immigration figures.

Many councils believe they are being short-changed because the statistics do not accurately reflect the reality.

This year the official estimate of London's population fell from 7,517,700 to 7,457,400.

But councils say the actual population is nearer to 7,600,000 because of the number of economic migrants, mainly from Eastern Europe.

Sir Simon Milton, the leader of Westminster City Council, says the council does not believe the official figures, especially when anecdotal evidence suggests there are 2,000 migrants arriving at Victoria coach station every week.

Merrick Cockell, leader of Kensington and Chelsea council, also said official figures were not credible.

Councils receive around £600 for every person in the borough from central government. They have warned that the miscalculation in the statistics could lead to council tax rises of £27 a head for Londoners.

In his speech, Mr Khan praised the Chief Constable of Cambridgeshire, Julie Spence, who last week warned that the rise in the number of Eastern Europeans to Britain had placed additional pressures on policing.

Mr Khan said the main challenge facing the Government was the way in which the police and local authorities received funding.

He said the revenue handed to councils from Whitehall "failed to recognise" the number of migrants and their families.

This was "a real problem" for local authorities, many of whom suffered from a "negative fiscal impact" as a result.

Mr Khan, one the most senior Muslim politicians in the country, also criticised some of his Labour colleagues for shying away from a public debate on migration.

"I think the Left have given the impression that there are no down-sides to migration," he said.

"We should treat people who have concerns about migration ... with the respect they deserve and we should try to address this in a mature and helpful manner."

He stressed that immigration had been hugely beneficial to Britain both culturally and economically.