The Conservatives have been accused of reheating pledges to jail illegal immigrants to distract from figures expected to show net migration to the UK is at its highest ever level.

Labour said that ministers were trying to "look tough" ahead of confirmation that they have spectacularly failed to meet their own immigration targets.

David Cameron has said that he wants to cut the numbers to the tens of thousands.

Official statistics show that in 2014 net long-term migration - the number of people entering the country minus the number leaving - totalled 318,000.

Only a small increase would be needed to surpass the highest figure on record, 320,000 in the year to June 2005.

Analysts at The Migration Observatory at the University of Oxford also predict that the figures will show that Britain's foreign-born population has passed eight million for the first time.

Data from 2013 shows there were 7.9 million people born overseas living in the UK.

The new Immigration Bill, due to be introduced in the autumn, could see illegals migrants caught working in the UK sentenced to up to six months in prison.

Late -night takeaways and off-licences could also be shut if they are caught employing staff no legal right to be in the UK.

The Conservative government has faced heavy faced in recent weeks criticism for its handling of the migrant crisis in Calais.

Madeleine Sumption, director of the Migration Observatory, said: "Given that we know net migration has been running in the hundreds of thousands since 2013, it would be surprising if the foreign-born population didn't go above eight million.

"The numbers have gone up steadily over time."

David Hanson, Labour’s shadow immigration minister, said: “This is the third time the Government have ?announced forms of these plans which have yet to be scrutinised by parliament in the as yet unpublished Immigration Bill. They are simply trying to look tough before Thursday’s migration figures and in the wake of failures at Calais.

“When these proposals finally come before Parliament, ministers need to explain how they will work in practice, how they will be enforced and why they won't extend gangmaster legislation to tackle traffickers at source."