All 27 European Union leaders have signed off on a final communique, issued on Thursday, outlining two options for Brexit that safeguard its own elections for a European Parliament.

Key points: The EU is trying to prevent the UK from being in the bloc during its parliamentary elections

The EU is trying to prevent the UK from being in the bloc during its parliamentary elections If Britain stays in the EU beyond May 22, it could invalidate the new EU parliament

If Britain stays in the EU beyond May 22, it could invalidate the new EU parliament The May 22 exit date is conditional on British MPs passing Mrs May's deal next week

The first option will grant Westminster an extension of Brexit to May 22 if the House of Commons passes British Prime Minister Theresa May's deal next week.

Otherwise, Britain would be given until April 12 to inform the bloc whether it will participate in European Parliament elections from May 23 – 26.

However, Mrs May has already indicated a lack of political appetite to force Britons to vote in EU elections.

The EU is keen to prevent Britain remaining in the bloc during the elections, as legal advice has said any new parliament may be invalid if Britain doesn't stage a poll.

If the EU does not to receive direction by April 12, its will let Britain fall out of the bloc without a deal.

European Council President Donald Tusk said he had spoken to Mrs May and she had agreed to the bloc's plan for a Brexit delay.

May rules out participation in 2019 EU elections

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 47 seconds 1 m 47 s Mrs May said it would be "wrong" to ask voters to vote in elections for a parliament they voted to get out of.

This week, Mrs May finally acknowledged the Brexit gridlock and asked the EU to delay Britain's departure until June 30, to create time to win parliamentary approval for her deal in a third attempt and then pass the legislation necessary for a smooth departure.

But opposition to her agreement among British MPs appeared to be hardening, rather than softening, after she blamed Parliament for the Brexit impasse.

In a televised address Wednesday night, Mrs May accused lawmakers of "infighting", "political games" and "arcane procedural rows", but acknowledged no personal error in creating the deadlock.

Pro-remain Conservative MP Anna Soubry, of the breakaway Independent Group, described it as the "most dishonest and divisive statement from any prime minister".

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Mrs May struck conciliatory note at a late-night Brussels news conference:

"I know MPs on all sides of the debate have passionate views, and I respect those different positions.

"Last night I expressed my frustration. I know that MPs are frustrated, too. They have difficult jobs to do," she said.

But Mrs May also refused to change course, calling on colleagues to back her agreement and refusing to rule out a no-deal exit if they did not back her.

Mrs May said that if the deal fell, by April 12, "we would either leave with no deal, or put forward an alternative plan" that involved participating in EU Parliament elections.

"I believe strongly that it would be wrong to ask people in the UK to participate in these elections three years after voting to leave the EU," she said.

President Macron has put the onus on British MPs in the next stage of the Brexit process. ( AP: Francisco Seco )

French President Emmanuel Macron said the European Council's dual offer to Britain was protecting the bloc's interests and would allow it to "continue working properly".

"Now it is finally up to the British political system," Mr Macron said, adding that any final decision must come ahead of the May 23 – 26 European Parliament election.

He would not speculate on whether he believed the British Prime Minister could win a third vote on the deal but said he wanted "to try and help Theresa May as much as possible".

EU coffers will suffer minimal impact if Britain crashes out

A "no-deal" scenario would trigger a major upheaval in trade and foreign relations that would damage Britain and continent, possibly greatly.

Ireland is set to lose the most out of Brexit, with predictions that its gross domestic product (GDP) will shrink by 1 per cent, in addition to fears that the return of a political border between the Republic of Ireland and Northern Ireland may trigger dormant sectarian violence.

However, contrary to some predictions, the EU27's economy will not suffer the almost 6 per cent drop in GDP predicted for Britain, with Germany, France, Italy and Spain's GDP losses sitting between 0.16 per cent and 0.18 per cent.

In Britain, taxis have been organised to collect MPs as the Deputy Speaker Lindsay Hoyle voiced fears of violence, while the Ministry of Defence has made 3,500 troops ready as part of "Operation Redfold", in the event of a no-deal Brexit, the BBC reported.

'Somewhat chaotic': Irish Taoiseach

Somewhat chaotic? British MPs have been told not to travel alone due to safety fears. ( Reuters: Henry Nicholls )

Mrs May's chances hang in the balance, with positions hardening after a chaotic week when the Parliament's speaker questioned whether she could even bring her deal to a third vote.

Northern Ireland's Democratic Unionist Party (DUP), which gives May's government a majority in Parliament, said it was no closer to backing her agreement, the party's Brexit spokesperson said on Thursday, while parliamentary Eurosceptics also said they could never approve something they said would trap Britain in the EU's orbit indefinitely.

In a challenge to Mrs May, opposition Labour leader Jeremy Corbyn was also in Brussels, speaking to EU officials about his alternative plan for Brexit, which he says could be negotiated during an extension and pass through parliament.

British Labour Party leader Jeremy Corbyn, right, has told EU leaders that his alternative plan could be passed. ( AP: Frank Augstein )

The Irish Prime Minister Leo Varadkar, officially known as the Taoiseach, summed up the situation in London, with no little understatement, as "somewhat chaotic".

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"We need to cut the entire British establishment a little bit of slack on this and support their request ... for a short extension," he told reporters

European Commission head Jean-Claude Juncker said the EU had done much to accommodate Britain and could go no further.

"If that doesn't happen, and if Great Britain does not leave at the end of March, then we are, I am sorry to say, in the hands of God," he said.

As Brexit is sapping EU resources, the leaders will also turn to other pressing issues later in the week, including the state of their economies, ties with China, climate change and ringfencing the European elections from illegitimate interference.

ABC/wires