The Home Office does not know whether foreign workers are leaving the UK or staying to work illegally after their visas expire, a cross-party committee of MPs has said.
The Public Accounts Committee (PAC), which scrutinises government spending, said the Home Office had failed to analyse exit checks since the skilled worker visa route was introduced in 2020 under the Conservatives.
Some 1.18 million people have applied to come to the UK via this route between its launch in December 2020 and the end of 2024.
The Home Office said earlier this year that it was working to modernise border security and boost digital checks. The BBC has approached the Home Office for comment on the report.
The skilled worker visa route replaced the Tier 2 (General) work visa after the UK left the European Union.
The route was expanded in 2022 by the previous Conservative government to address skill shortages and job vacancies in health and social care in the wake of the Covid pandemic, driving net migration to record levels.
But the PAC has accused the Home Office of failing to gather "basic information" on whether people leave the UK after their visas expire and showing "little curiosity about how the route was operating".
Its report said the department still relied on airline passenger records to check if someone had left the country and that there had been no analysis of those records since 2020.
It added that the Home Office needed to set out what measures would be put in place to record when people had left the country.
The report also said there was "widespread evidence of workers suffering debt bondage, working excessive hours and exploitative conditions" and accused the department of being "slow and ineffective" to tackle exploitation.
In May, Home Secretary Yvette Cooper said the government would end overseas recruitment for care workers as part of the plans to curb near record net migration.
Home Office Permanent Secretary Dame Antonia Romeo has also said overstaying is a "problem" the department was "fixing".