Home Secretary Theresa May is facing demands for an urgent statement to Parliament amid the "confusion" over the Government's latest bid to deport the terrorist suspect Abu Qatada.
Lawyers for the radical cleric have lodged an appeal with Europe's human rights judges following his rearrest on Tuesday, effectively putting moves to return him to stand trial in his native Jordan on hold.
Last night the government insisted it had calculated the deadline date correctly and said its lawyers had written to the ECHR arguing the appeal should not be heard.
A Home Office spokesman said: "A letter was sent yesterday arguing the case should not be referred to the Grand Chamber of the court because the deadline of appeal had elapsed."
Officials in Strasbourg are yet to respond.
Mrs May dismissed the appeal as a "delaying tactic" - insisting the deadline passed on Monday - three months after the European Court of Human Rights (ECHR) ruled he could be returned.
However, after the court refused to confirm that the Home Office had calculated the deadline correctly, shadow home secretary Yvette Cooper said she must return to the Commons to explain what had happened.
"We need urgent clarification from the Home Secretary on whether she got the timing wrong," Ms Cooper said.
"The Home Office are saying one thing, the European Court another. Why didn't they just agree the deadline in advance so there could be no opportunity for Abu Qatada or his lawyers to exploit?
"Everyone wants Abu Qatada deported and held in custody in the meantime, in line with the security assessment agreed by the Government and courts. But we don't want to see that jeopardised by confusion at the Home Office."
"The Home Office are saying one thing, the European court another. Why didn't they just agree the deadline in advance so there could be no opportunity for Abu Qatada or his lawyers to exploit?
"We said to Theresa May yesterday that there seemed to be a troubling level of confusion over this process, and so it has proved." Cooper told The Guardian.
Meanwhile the row over Qatada's deportation was described as "chaotic and almost farcical" by Keith Vaz, the chairman of the Commons home affairs select committee.
A miscalculation of the deadline would be a massive embarrassment for Mrs May and could again set back the authorities' long-running battle to put Qatada on a plane out of the country.
However In a round of media interviews on Wednesday, Mrs May was adamant that the time for an appeal ran out at midnight on Monday.
"This is a delaying tactic from Abu Qatada," she said.
"As you would expect, we have been in touch with the European court over the last three months to check our understanding. They were absolutely clear that we were operating on the basis that it was midnight on April 16."
A spokeswoman for the Strasbourg-based court said Qatada's appeal was lodged at 11pm local time (10pm BST) on Tuesday, but added: "We cannot comment on the view taken by the UK authorities about when the deadline expired."
She added: "The fact that we have received a referral request means that the chamber judgment is not final and that the Rule 39 injunction against removal remains in force.
"A panel of the court will decide whether to accept or reject the appeal soon."
Prime Minister David Cameron has expressed his determination that Qatada would eventually be deported, no matter how long it took.
"I am absolutely clear, the entire government is clear, and frankly I think the country is clear, that this man has no right to be in our country.
"He is a threat to our security, he has absolutely no further call on our hospitality and he should be deported.
"That is what we are determined to achieve, no matter how difficult it is, no matter how long it may take,"
The latest appeal is separate from any others that Qatada's legal team may make over the decision by Mrs May to continue with his deportation after receiving assurances from Jordan that evidence gained through torture would not be used against him.
Instead it relates to a different strand of the original decision of the Strasbourg-based court which found that the 51-year-old could be sent back to Jordan with diplomatic assurances that he would not be tortured.
He is currently behind bars after a senior immigration judge ruled his imminent deportation meant the risk he could try to flee while on bail had increased.
But his lawyers have said they will challenge all moves to deport him and Mrs May has warned MPs that it may still be "many months" before Qatada can be lawfully kicked out.
Qatada, who is said to have "wide and high-level support" among extremists, was convicted in his absence in Jordan of involvement with terror attacks in 1998 and now faces a retrial in his home country.
He also featured in hate sermons found on videos in the flat of one of the September 11 bombers.
Since 2001, when fears of the domestic terror threat rose in the aftermath of the attacks, he has challenged, and ultimately thwarted, every attempt by the Government to detain and deport him.