New households overall will rise from 223,000 a year to 246,000. New migrant homes will account for 39 per cent of those.

The report concludes: “The overall economic benefit of migration is small and heavily outweighed by the implications of adding 18million to our population in the next 50 years.”

The think-tank will present its findings tomorrow to the House of Lords Economic Affairs Committee, which is examining the impact of immigration, after evidence from Immigration Minister Liam Byrne.

Houses are allocated on a need basis, meaning immigrants are often more likely to be given a property as they are frequently newly arrived in the country with nowhere to live. In 2006 immigrants were handed 10,000 council homes worth £1.3billion, with the Government paying almost half that amount. The remainder was funded by housing associations and developers.

The Government’s equality chief Trevor Phillips recently said the fear that migrants are jumping council queues for homes is fuelling tensions.

The Migrationwatch report also attacks what it calls the Government’s “four favourite fibs” on the benefits of immigration. It dismisses claims that migrants are needed to fill 600,000 job vacancies – because around 900,000 people have come since 2001 but the vacancies remain the same.

It rejects suggestions that immigrants account for eight per cent of the workforce but contribute 10 per cent of gross domestic product, and attacks claims that immigrant earnings are 13 per cent higher than those of indigenous workers. And claims that our pensions depend on immigrants were rejected by the Lords committee five years ago, it says.

The report comes as around a million migrants gather on the coast of Libya planning a sea crossing to Europe, some hoping to head for the UK.

Of up to two million migrants living there, about half are using it simply as a staging post to get to Europe, the International Organisation for Migration will claim in BBC1’s Panorama tonight.

Of the 30,000 migrants who made it from Africa to Europe last year, about two-thirds used the Libyan route.

There are growing fears that Labour’s open-door policy is putting an increasing strain on already overstretched resources.

Britain’s population could virtually double in a lifetime due to soaring immigration and rising birth rates, figures showed last year. Numbers could top 110million by 2081, the Government Actuary’s Department said.

The number of children born to Eastern Europeans in Britain has soared 100 times faster than those born to British mothers, figures showed in November.

The Daily Express told last week how one in eight pupils does not speak English as a first language after the number of non-English-speaking new pupils soared 50 per cent in just two years.

English is now the minority language in one in 17 schools.

The Home Office said yesterday: “There are legitimate concerns about managing some of the effects of migration on communities. We are listening to these concerns.

“It is why we are bringing sweeping changes to the immigration system, including the introduction of an Australian-style points-based system so only those Britain needs can come to work and study. It is also why we are maintaining restrictions on Bulgarian and Romanians.

“The Migration Advisory Com-mittee is advising us on how migration can sensibly fill skills shortages.”