Lord Kerr said that Article 50 can be reversed and “we can change our mind at any stage of the process” during a speech at an Open Britain event in London today.
He said that the just because Theresa May sent the Article 50 letter in March 2017, it does not mean Britain has no choice but to leave in March 2019.
He added: “Mrs May’s letter was only a notification of the UK’s “intention” to withdraw. Intentions can change.
“We still have all the rights of a member-state, including the right to change our minds.”
Lord Kerr, a former UK ambassador to the EU, said that Article 50 of the Lisbon Treaty was not drafted to say that Article 50 notification letter is irrevocable.
He added: “So, the die is not cast irretrievably. The letter can be taken back.”
The speech came just after Theresa May confirmed plans to amend the withdrawal bill to ensure that Britain leaves the EU on March 29 2019.
In March 2017, Mrs May triggered Article 50 – the step that started the timer on two years of EU exit talks before the UK must leave the EU.
In the Telegraph today, the Prime Minister said: “Let no one doubt our determination or question our resolve, Brexit is happening.
“It will be there in black and white on the front page of this historic piece of legislation: the United Kingdom will leave the EU on March 29 at 11pm GMT.”
There remains uncertainty over whether it is legally possible for the UK to reverse Article 50 because it is not set out in the clause.
Open Europe policy analyst Aarti Shankar said: “From a legal standpoint, it is extremely unclear what the legal basis for revoking Article 50 would be. It would, I think, fall to the European Court of Justice to decide.
“But if it were possible, it is highly unlikely that it could be unilaterally revoked by the UK – it would require unanimous agreement from the EU27.
“And it is not self-evident that they would consent, particularly if talk of revocation came closer towards the end of the Article 50 timeframe – the pressure of a two-year ticking clock is the EU’s most important leverage in negotiations.”
But she said: “The government has given no indication of its intention to withdraw its Article 50 notification, and has previously argued tis legal position is that Article 50 is irrevocable – so questions of revocability fall beside the point I think.”
In a debate over Article 50 in January, David David said they view the EU referendum result on June 23 2016 as the “irrevocable moment”.
“It is not in the gift of the Government to change their mind, so we have already passed the point of no return,” he added.
In March Professor Catherine Barnard, senior fellow at The UK in a Changing Europe, said it is not known if the UK can revoke Article 50 from a legal point of view.
She said: “The answer is no-one knows because the Article does not make this clear and it has never been tested before but most lawyers think once triggered the Article 50 process can be reversed.”
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