Negotiations on a new treaty with Rwanda over the UK’s stalled deportation policy are in their final stages, according to the Home Office’s top civil servant.

Permanent secretary Sir Matthew Rycroft told MPs officials were in the capital Kigali “as we speak” as they put the “finishing touches” to the talks after the Supreme Court ruled against the plan to send some asylum seekers on a one-way trip to the African nation.

The Government now faces questions over how much it has already paid Rwanda and if more payments are due to be made, after MPs were told they would have to wait months to learn if it was more than the £140 million previously disclosed.

Sir Matthew hinted more cash could be paid but would not say if any additional payments had since been made when pressed on the matter, instead saying ministers had decided they would not reveal that information until the summer.

Speaking to the Commons Home Affairs Committee on Wednesday, he said: “The negotiation of that treaty is ongoing. In fact, there’s a Home Office and wider team in Kigali as we speak, putting the finishing touches to that negotiation. And I think it’d be premature to say anything about the content of that.”

His comments come a day after Downing Street said Rishi Sunak was still considering how to make sure the plan was legally watertight amid reports Government lawyers warned attempting to opt out of international rights treaties could delay flights.

The Government promised a treaty with Rwanda and emergency legislation in Parliament after the Supreme Court ruling.

No 10 had said in the hours after the court defeat on November 15 that the treaty would be laid before Parliament in the “coming days” so deportation flights could take off “as soon as possible”.

But the Prime Minister’s official spokesman said policy options were still being considered, although the Government still hopes the first flights will take off by the spring.

Asked by committee chairwoman Dame Diana Johnson whether “anything else had been given to the Rwandan government”, in addition to the confirmed £140 million, he replied: “So there are additional payments each year and ministers have decided that the way to keep you and other colleagues in Parliament updated is once a year to set out the total additional payments to the government of Rwanda.

Prime Minister Rishi Sunak
Prime Minister Rishi Sunak promised a treaty with Rwanda and emergency legislation in Parliament after the Supreme Court ruling earlier this month (Leon Neal/PA)

“And we’ll do that in the annual report and accounts. So the figures that you set out, the £120 million (initial payment when the deal was initially signed) plus £20 million are the payments from the 2022 to 2023 financial year and then any payments in 2023/24, we will announce in the normal way in the next annual report.”

Asked again to confirm whether any further payments had already been made, Sir Matthew said: “We will announce that in the normal way next summer.”

Dame Diana said his responses made it “quite hard to effectively scrutinise the flagship policy of the Home Office, and how much money is being spent on it, when we’re only getting the figures at the end of the year.”

To which Sir Matthew replied: “Ministers have decided that the way to update Parliament is annually, rather than giving a running commentary.”

Labour’s shadow minister for immigration Stephen Kinnock described suggestions that Britain could sent more money to Rwanda, despite no migrants being sent there yet, as an “affront to the hard-working British taxpayer”.

Sir Matthew told MPs he did not know how much the Government’s legal battle over the deal cost and would respond to the committee at a later date, saying it was “not realistic” to say how many Home Office officials were working on the policy as they “are doing other things as well”.

Several MPs expressed their exasperation at the lack of detail Sir Matthew was able to provide.

Following a series of exchanges on various subjects, including Channel crossings and removing failed asylum seekers from the UK, where Sir Matthew and his second-in-command Simon Ridley were unable to answer questions, Dame Diana asked: “Do we have any figures about anything?”

Committee member Lee Anderson later added: “I find this absolutely staggering that the big boss hasn’t got a clue, not just on this question, but nearly every other question we’ve asked today. Why is that?”

“Mr Ridley is looking for the numbers and we will send them to you”, Sir Matthew replied.