The alleged economic benefits to Britain of record levels of immigration are a myth, new figures suggest.

They show a ''very slight" gain of around 4p a week for each member of the native population — not enough to buy a Mars bar a month.

An analysis carried out by Migrationwatch UK used the Government's own claim that immigrants contribute a net £4 billion a year to Britain's gross domestic product.

The study said this amounted to £2.10 a year for each of Britain's 60 million inhabitants.

It concluded: "The much vaunted contribution of immigrants to the economy is very slight indeed."

Sir Andrew Green, the chairman of Migrationwatch, said: "Of course many immigrants make a useful contribution to the economy but, taken in total, the economic benefit is at best marginal.

''The main beneficiaries are the immigrants themselves who are able to send home about £10 million a day, not the host nation."

He added: "The Government seek to present the record immigration levels as being nothing but good news for the host community as a means of deflecting attention from some of the many problems it is causing, and to neutralise the deep public disquiet they know is out there."

Migrationwatch examined a range of British and international studies on the economic value of mass immigration, all of which indicate that, on a per capita basis, the financial benefits are minimal.

In addition, high levels of immigration place huge pressure on housing, health and schools and have an increasing impact on employment.

Sir Andrew said: "If we are to have the mature and thorough debate that ministers have been calling for let us start off with an honest assessment of the costs and benefits of the highest levels of immigration in our history."

Critics of high immigration argue that while such levels are attractive to employers because they provide cheap labour, they are expensive for the taxpayer and harmful for less-skilled indigenous workers whose wages are held down.

A Home Office spokesman said: "Overall, migration is good for employment and good for the economy.

"The Treasury estimates that migration accounts for 10-15 per cent of trend growth, and independent research has found that migrants make a net contribution to the Exchequer."

But David Davis, the shadow home secretary, said: "The figures in this report contrast sharply with what the Government claim and betray a chronic deficit of information on immigration."