Plans to enshrine the exact date and time of Brexit could harm the UK’s negotiating strategy, a cross-party group of senior MPs has said.
The Brexit Select Committee warned there could be “significant difficulties” if the Government passes its single amendment to the EU Withdrawal Bill.
Members said it was important to “maintain flexibility” to secure a deal.
Hilary Benn, who chairs the committee of 21 MPs from six political parties, said in a report published on Friday: “We need to maintain flexibility as the negotiations proceed.
“But ministers are now proposing to remove from the Bill the power to set different exit days for different purposes and replace it with a single exit day – 11pm on 29 March 2019.
“This would create significant difficulties if the negotiations were to continue until the 59th minute of the 11th hour, as the Secretary of State suggested to us might happen.”
Last month, David Davis said EU divorce talks could go on until the last stages of membership – admitting a deal could be secured as late as March 2019.
The Government is already facing opposition from pro-Remain Tories to the amendment it tabled to its flagship Brexit bill.
Former attorney general Dominic Grieve called the move “incoherent and thoroughly stupid”, prompting a senior Cabinet minister to hint it could be dropped.
But Downing Street remained adamant they would not U-turn, with a spokesperson saying: “What the amendment does is provide certainty over our position that we are leaving the EU on 29 March 2019. We would encourage all MPs to support it.”
Asked if the PM was confident of getting the amendment passed, they said: “Yes.”