Published: 5:44 AM April 11, 2019 Updated: 6:01 PM September 17, 2020

Prime Minister Theresa May holds a news conference after the European Council in Brussels. Photograph: Stefan Rousseau/PA Wire. - Credit: PA

The UK could be heading for a Halloween Brexit after the remaining 27 EU nations offered Theresa May a further six months to ratify or rethink her withdrawal deal.

The second extension to the Brexit process - initially intended to conclude on March 29 - definitively stopped the clock on a no-deal withdrawal on Friday with less than 48 hours to go.

In an early-hours press conference, European Council president Donald Tusk did not rule out further extensions beyond October.

And he sent a message to the UK: 'This extension is as flexible as I expected, and a little bit shorter than I expected, but it's still enough to find the best possible solution.

'Please do not waste this time.'

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Addressing the press shortly before 2am, May said that she still wanted the UK to leave the EU 'as soon as possible'.

If a withdrawal deal could be ratified within the first three weeks of May, the UK could still avoid participation in that month's European Parliament elections and leave the EU in June, she said.

Acknowledging 'huge frustration' among voters that the UK has not yet left the EU, she said: 'The choices we now face are stark and the timetable is clear.

'So we must now press on at pace with our efforts to reach a consensus on a deal that is in the national interest.'

Talks between the government and Labour to find a compromise way forward will continue at official level on Thursday.

'I do not pretend the next few weeks will be easy or that there is a simple way to break the deadlock in Parliament,' said May.

'But we have a duty as politicians to find a way to fulfil the democratic decision of the referendum, deliver Brexit and move our country forward. Nothing is more pressing or more vital.'

The six-month extension was a compromise solution thrashed out in five hours of talks in Mrs May's absence, after French President Emmanuel Macron held out against a longer extension lasting into 2020.

Under the terms of the agreement, the UK can leave at any time if the Withdrawal Agreement reached last November is ratified by the Westminster Parliament.

If the UK fails to take part in elections to the European Parliament on May 23-26, it will automatically leave without a deal on June 1.

A review of progress will take place at the scheduled June 20 European Council summit in Brussels, but Tusk stressed that this would be an opportunity for 'taking stock' and not for any new negotiations.

The term of the current European Commission under Jean-Claude Juncker ends on October 31.

A UK exit by that date would get round the diplomatically awkward requirement for London to appoint a new Commissioner to his successor's team.

But asked whether a further extension might be possible, Tusk replied: 'Our intention is to finalise the whole process in October... but I am too old to exclude another scenario. I think still everything is possible.'

US president Donald Trump invoked America's trading relationship with the EU in his assessment.

He tweeted: 'Too bad that the European Union is being so tough on the United Kingdom and Brexit. The E.U. is likewise a brutal trading partner with the United States, which will change.

'Sometimes in life you have to let people breathe before it all comes back to bite you!'

Chuka Umunna, spokesman for The Independent Group of breakaway MPs, said the extension provided an opportunity for a second referendum.

He said: 'Unless the main party leaders do a backroom deal to enable a customs union Brexit and deny the British people a say over this mess - a big risk - this extension paves the way for Euro elections +a £PeoplesVote which we must grab with two hands for the sake of future generations.

'With British MEPs continuing to sit in the Euro Parliament we will be rule makers not rule takers - if Brexit had happened and the UK was in transition, it would have been the opposite. A #PeoplesVote with Remain on the ballot will give voters a chance to make this permanent.'

Liberal Democrat MP Sir Ed Davey also called for a second referendum to be held.

'Tonight we breathe a sigh of relief: our EU friends offer us escape from 'BrexitShambles,' he tweeted.

'Enjoy the moment: a key step in a long journey. Tomorrow we push #PeoplesVote even harder.

'Let's get this nightmare behind us & pull UK back together'.

Labour MP Mary Creagh, a supporter of the People's Vote campaign for a second referendum, said she hoped for 'sincere cooperation' on Brexit from the government 'after this fiasco'.

She said: 'People across the UK will be relieved at this sensible extension.

'Parliament must agree tomorrow and MPs must move swiftly to break the Brexit deadlock with a confirmatory ballot on the PM's deal.'