It also gives warning that ministers may be forced to abandon their refusal to grant housing and welfare benefits, creating what it describes as an extra “pull factor”, attracting further immigrants.

The arrival of hundreds of thousands from abroad is already forcing down wages for low-paid workers with “serious implications” for social discord, the report insists. A “step change” in the level of immigration when Romania and Bulgaria join the EU next year could make things worse, it says.

The document, by the junior Home Officer minister Joan Ryan and entitled Migration From Eastern Europe: Impact on Public Services and Community Cohesion, reveals that every government department has been ordered to draw up contingency plans to deal with the extra pressure on schools, housing and health.

The report says that schools will be under pressure, with thousands of children arriving here unable to speak English.

It insists that hospitals will struggle to cope with Eastern European patients who “block” hospital beds because they are ineligible for social care and benefits if they leave.

The report also reveals that towns and cities where large numbers of the new immigrants have settled are demanding millions of pounds of extra money to cope.

The leaked document, marked “Restricted”, was written by Ms Ryan on July 19, the day after she submitted a report saying that 45,000 “undesirable” criminal migrants from Romania and Bulgaria may settle in Britain next year.

The report also insists that, although foreign workers have filled jobs that British workers do not want to do, there is evidence that wages for low-paid workers have been affected.

It says: “There is anecdotal evidence, particularly from Southampton, a port of entry for Eastern Europeans, that the effect of migration . . . has been to depress wages for low-paid workers. If this were widely true, or that perception were to spread widely, the implications for community cohesion would be potentially serious.”

Ms Ryan is concerned that a legal challenge could force the Government to abandon restrictions on Eastern European immigrants applying for benefits and social housing. Her report says that some councils are demanding an end to this restriction so that they can get them off the streets.

The Government is already being criticised for underestimating the flood of migrants from eight former Soviet bloc states that joined the EU in 2004: some 662,000 came to Britain in the past two years, instead of the 10,000 to 26,000 predicted. Ministers expect that number to rise by up to 140,000 next year.

The leak coincided with a police report yesterday revealing that the migration of East Europeans to the UK is bringing mafia-style gangsters and organised prostitution to rural areas. The document, an unlisted appendix to a council meeting in Cornwall, cites figures from Boston, Lincolnshire, where there are large numbers of migrant workers.

In Boston, the report notes, “the local community have reacted adversely” to “drinking, noise and the open proliferation of massage parlours”.

A recent police stop-and-check in Lincolnshire found 50 per cent of all drivers were committing an offence and 97 per cent of those were migrant workers.

The document notes: “There has also been a marked increase in road traffic accidents in this rural area. There is a real concern over safety issues as a consequence.”

It reports that in Boston there is a “rapid increase” in bulk buying of new homes for “labour providers” to house their low-paid workers. The report says: “This has fuelled demand and price inflation. The council estimates the average two-bedroom house price has risen 400 per cent in six years. There has been ‘ghettoisation’ of some areas. Surprisingly, this is not just in older housing areas: but also on new-build estates, where blocks of property are being bought direct from developers.”

The report was drawn up by Kerrier council, in Cornwall, where an estimated 2,500 migrants fill jobs in agriculture, fishing and catering.

Police also revealed yesterday that illegal immigrants are being smuggled into Britain from France for less than £150 a head. The disclosure by the low-profile Serious Organised Crime Agency (Soca), set up four months ago, was far less than any fee previously mentioned in relation to people smuggling. It emerged in Soca’s “threat assessment” of serious and organised crime in the UK.

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