The Conservatives’ Rwanda scheme cost taxpayers £700m, Home Secretary Yvette Cooper has said.
The previous government had planned to send some asylum seekers to Rwanda to deter people from crossing the Channel in small boats.
However, the scheme was stalled by legal challenges and Ms Cooper said only four people had been removed to the country voluntarily.
Labour has said it is scrapping the scheme, describing it as an “expensive gimmick”.
Shadow home secretary James Cleverly accused his counterpart of using “made up numbers”.
Giving a statement in the Commons, Ms Cooper said the figure of £700m included £290m of payments to Rwanda, the cost of chartering flights that never took off, detaining hundreds of people and then releasing them, as well as paying for more than 1,000 civil servants to work on the scheme.
“A scheme to send four people, it is the most shocking waste of taxpayers’ money I have ever seen,” she said.
“Looking forward, the costs are set to get worse. Even if the scheme had ever got going it’s clear it would only cover a minority of arrivals, yet a substantial portion of future costs were fixed costs.”
Ms Cooper added that over six years the government had planned to spend more than £10bn of taxpayers’ money on the scheme.
However, Mr Cleverly accused Ms Cooper of “hyperbole” and “made up numbers”.
He claimed Labour had scrapped the Rwanda scheme on “ideological grounds”, arguing it was needed as a deterrent.
He added: “The level of discourtesy, directed towards the people and government of Rwanda is quite breathtaking.
“To have them read about this decision in the papers before anyone from government had the good grace to formally notify them, I think, is an error, and no one in this House believes for a moment that that level of discourtesy would have happened had this partnership been with the European country.”
Ms Cooper said by scrapping the scheme the government would save £220m on further direct payments to Rwanda over the next few years, as well as up to £750m that has been put aside to cover the scheme this year.
The home secretary said some of the money saved would be invested in a new Border Security Command, bringing together Border Force officials, police and intelligence agencies to tackle people-smuggling gangs.
She added that Home Office staff were being redeployed from the scheme to work on enforcement and returning failed asylum seekers.
The UK government previously said it was looking carefully at what money could be recouped after scrapping the scheme.
However, the Rwandan government has said it is under “no obligation” to refund any money.
