MPs are set to be summoned or a special Saturday sitting of Parliament next week after the crucial EU summit.

Government sources said the session is expected to take place regardless of whether Boris Johnson has been able to secure agreement on a Brexit deal. The European Council summit on next Thursday and Friday is the last scheduled meeting of EU leaders before Britain is supposed to leave on October 31.

If the Prime Minister is able to get an agreement, it will allow MPs – who will have to give their approval – to debate it.

If he fails, Johnson is expected to set out how he plans to take Britain out of the EU at the end of the month regardless.

READ MORE: Court of Session delays decision on extension letter

The prospects of an agreement were looking slim after Downing Street accused the EU on Tuesday of making it "essentially impossible" for the UK to leave with a deal. European Council President Donald Tusk responded by saying Johnson should acknowledge the seriousness of the situation rather than playing "stupid blame games".

Johnson is expected to meet Irish Premier Leo Varadkar on tomorrow in a last-ditch effort to break the deadlock over the Northern Ireland backstop. But after speaking to Johnson by telephone on Tuesday, Varadkar warned that it would be "very difficult" to get an agreement in time for next week.

While the Irish Government and the EU were working to get an agreement, he said they were not prepared to do a deal "at any cost".

"There are some fundamental objectives that haven't changed for the past three years and we need them guaranteed," Varadkar told RTE news. "I think it is going to be very difficult to secure an agreement by next week, quite frankly.

"Essentially what the United Kingdom has done is repudiate the deal that we negotiated in good faith with Theresa May's government over two years and sort of put half of that now back on the table and are saying 'That's a concession'. And of course it isn't really."

The meeting with Varadkar comes in the wake of a series of acrimonious exchanges between London, Dublin and Brussels.

Number 10 sources have accused the Irish premier of going back on a commitment to find a deal by the end of October. There was also a "frank" exchange of views between Johnson and German Chancellor Angela Merkel in a phone call on Tuesday.

READ MORE Senior European politician hits out at UK's 'odious' threat on security

Afterwards, unnamed Downing Street sources claimed Merkel had made clear an agreement was "overwhelmingly unlikely".

She was said to have told Johnson that if the UK was leaving the EU, it would have to leave Northern Ireland behind in a customs union.

European Commission president Jean-Claude Juncker said that if the negotiations failed, "the explanation will be found in the British camp (because) the original sin is found on the islands and not on the continent".

He told the French Les Echos newspaper that in such an event, both sides would suffer.

"A no-deal Brexit would lead to a decline of the United Kingdom and a weakening of growth on the continent," Juncker said.