British Prime Minister Boris Johnson has said some MPs hoping to block Brexit were engaged in "terrible" collaboration with the European Union by undermining the British government's negotiating hand and so making no-deal more likely.

Hours after senior MPs said they would seek to prevent any attempt to ignore parliament over Brexit, Mr Johnson used a question-and-answer session on Facebook to attack them.

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Mr Johnson said that there "is a terrible kind of collaboration as it were going on between those who think they can block Brexit in parliament and our European friends. 

"We need our European friends to compromise and the more they think that there's a chance that Brexit can be blocked in parliament, the more adamant they are in sticking to their position." 

Mr Johnson's use of the word "collaborator" has historical echoes for British people, the term was used for people who cooperated with Nazi Germany during World War Two.

Speaking on RTÉ's News at One, former British Attorney General, Dominic Grieves said he doubts the alleged collaboration exists, adding that if it does he is not a part of it.

"The idea there is a collusive relationship between the EU and members of parliament is very far fetched," he said.

Mr Grieve said Mr Johnson only has himself to blame if he is finding it difficult to negotiate, saying it would be more sensible to "go and have an open negotiation that doesn't start with blood-curdling threats."

Mr Grieve also said that Mr Johnson has been "hoisted by his own petard".

"I simply don't know if he is prepared to take the UK out with no-deal. He has made it the centrepiece of his policy that he should be willing to do it and as a result he is hoisted on his own petard.

"He makes his own life most difficult and then turns around and blames Philip Hammond or myself."

Mr Grieve also agreed with claims made by the former chancellor of the exchequer, Philip Hammond, that unelected officials in Downing Street are influencing Brexit policy.

Mr Grieve said this is "obviously not very helpful" from the point of view of providing reassurance.

He also said that Dominic Cummings, Mr Johnson's policy adviser, has said some things that are "simply outrageous".

"Once you start embarking on populist, tub-thumping policies in the way he has been presenting them you start creating an echo chamber of more tub-thumping," he said. 

"For anybody who wants to take a reasoned approach you are in danger of being bulldozed out of the way so then you stand up and speak and then you are being accused of making it more difficult to achieve a compromise which it looks as if the Prime Minister has long ago decided to abandon."

Listen: Dominic Grieve on RTÉ's News at One

Pelosi says Good Friday deal will be defended if threatened by Brexit

Earlier, former finance minister Hammond said that parliament will block a no-deal Brexit if unelected people behind Mr Johnson try to wrench Britain out on 31 October without agreement.

"The people behind this know that that means that there will be no deal," Mr Hammond told the BBC. 

He added: "Parliament is clearly opposed to a no-deal exit, and the prime minister must respect that."

The former minister's first public intervention since resigning indicates the determination of a group of influential MPs to thwart Mr Johnson if he goes for a no-deal Brexit.

Mr Hammond said he was confident parliament, where a majority oppose a no-deal Brexit, would find a way to block that outcome.

It is, however, unclear if MPs have the unity or power to use the 800-year-old heart of British democracy to prevent a no-deal Brexit on 31 October, likely to be the UK's most consequential move since World War Two.

Opponents of no-deal say it would be a disaster for what was once one of the West's most stable democracies. 

A disorderly divorce, they say, would hurt global growth, send shock waves through financial markets and weaken London's claim to be the world’s preeminent financial centre.

Brexit supporters say there may be short-term disruption from a no-deal exit but that the economy will thrive if cut free from what they cast as a doomed experiment in integration that has led to Europe falling behind China and the US.

Heading towards one of the biggest constitutional crises in at least a century, Britain's elite are quarrelling over how, when and even if the result of the shock 2016 referendum will be implemented.

Part of the problem is that Britain's constitution, once touted as a global model, is uncodified and vague. It relies on precedent, but there is little for Brexit.

The House of Commons speaker John Bercow told an audience in Scotland that lawmakers could prevent a no-deal Brexit and that he would fight any attempt to prorogue, or suspend, parliament "with every bone in my body".

Mr Johnson, who replaced Mrs May after she failed three times to get her Brexit deal through parliament, has refused to rule out proroguing the House of Commons and Brexit supporters have vociferously encouraged him to do so if necessary.

Mr Johnson's top advisor, Dominic Cummings, has reportedly said he could delay calling a general election until after 31 October, even if he lost a no-confidence motion, allowing for a no-deal Brexit while parliament is dissolved.

Clearly with him in mind, Mr Hammond said there were people "who are pulling the strings in Downing Street, those who are setting the strategy."