181,000 migrants 'in UK illegally'
Up to 181,000 migrants who should have gone home over the past two years alone could still be in the UK illegally, figures suggest.
The UK Border Agency (UKBA) estimate showed it does not do enough work to check that migrants leave the UK if they have no right to remain, said the National Audit Office (NAO).
But Immigration Minister Damian Green said the report showed exactly why radical reforms to the UK's immigration system were needed.
The auditors found migrants and employers could exploit the points-based system for visas because the UKBA has failed to check the risks posed by key features of the process.
They called for the UKBA to "give greater priority to ensuring that migrants leave when they should" and said it should set national targets to tackle those who overstay their visas.
"The agency estimates there may be up to 181,000 migrants in the UK of all visa types whose permission to remain has expired since December 2008," said the NAO.
It added that the UKBA "lacks the ability to easily identify individuals whose visas have expired".
Margaret Hodge, chairwoman of the Committee of Public Accounts, said that after the UKBA refuses extensions to visas, "it cannot guarantee that these people actually leave the country".
"The agency relies on employers to police their own employees and does not carry out its own checks," she said.
"There could be as many as 181,000 people here on expired visas."