One of the most important cross-party parliamentary committees says the Home Office does not have a credible plan to implement its Rwanda scheme for asylum seekers.

In a highly critical report, the Public Accounts Committee said the government’s accommodation plan had fallen “woefully short of reality”.

One site had cost 10 times more than the original £5m price tag.

So far, the government has spent £310m on the Rwanda scheme – and Prime Minister Rishi Sunak says there will be no flight before polling day.

According to the figures from the National Audit Office, the spending watchdog, £290m of the £310m spent so far has been given to the African country.

Those costs are on top of money spent on housing more than 50,000 asylum seekers in the UK, following a decision last year to halt consideration of whether any of them should be recognised as refugees and given permission to work.

“We are concerned that the Home Office does not have a credible plan for implementing the Rwanda partnership,” the committee said.

“There are currently more than 50,000 people who are deemed to be in the UK illegally, and that the Home Secretary will have a duty to remove.

“During our [evidence] session, the Home Office was unwilling to say how many people it is planning to relocate to Rwanda, and how it would do this.

“We are concerned by the Home Office’s inability to explain the practical details.”

Officials had told the committee there were robust operational plans – but the MPs said: “We are left with little confidence in the Home Office’s ability to implement the Rwanda partnership, and its understanding of the costs, particularly given its track record in delivering other major programmes.”

The 50,000 cross-English Channel migrants who are in limbo in the UK are living in Home Office-funded housing, hotel rooms and large accommodation sites, including two converted RAF bases.

But the committee said the new sites had cost far more than expected.

“We welcome the Home Office’s progress in closing asylum hotels in communities, but its assessment of the requirements for setting up alternative accommodation in large sites fell woefully short of reality and risked wasting taxpayers’ money,” it said.

The department had estimated it would cost £5m to convert RAF Wethersfield, in Essex, but so far it had spent £49m. RAF Scampton, in Lincolnshire, has so far cost £27m – and the committee warned the total bill for the new sites could be £46m higher than keeping the migrants in hotels.

Responding to the report, Home Secretary James Cleverly said: “People will only stop coming to the UK illegally when they know they won’t get to stay. Labour would strip Britain of that deterrent.

“The cost of housing asylum seekers will reach £11bn a year by 2026, which is why our Rwanda scheme is so important.

“Labour have no plan to stop the boats – they would scrap our Rwanda scheme and grant an amnesty to hundreds of thousands of illegal migrants with no right to be here.”

Labour says it has no amnesty plan and Yvette Cooper, the shadow home secretary, said the report “confirms the complete chaos behind Rishi Sunak’s Rwanda con”.

She said: “Rishi Sunak knows his gimmick won’t work to stop boat crossings – that’s why he has called an election, to prevent the entire scheme from unravelling.

“He is trying to take voters for fools – and wasting hundreds of millions of pounds of taxpayers’ money in the meantime.”