LONDON (BLOOMBERG) - Members of Boris Johnson's Conservative Party demanded Britain withdraw from the European Convention on Human Rights (ECHR) after a court ruling forced the Home Office to cancel its first deportation flight to Rwanda at the eleventh hour.

With the plane sitting on the tarmac, judges at the European Court of Human Rights in Strasbourg - which enforces the convention - halted the deportation of one of the men due for deportation. That triggered a series of legal challenges leading to the remaining handful of deportees to be withdrawn from the flight.

The move prompted fury among Tory MPs, some of whom demanded Mr Johnson leave the ECHR.

In a series of WhatsApp exchanges Tory MP Brendan Clarke-Smith called the issue "war" with the ECHR. His colleague Alexander Stafford called it a "disaster." Their comments were verified by a member of their WhatsApp group.

The rulings are the latest setback for Mr Johnson's flagship immigration policy, which involves sending to Rwanda migrants it regards as having arrived illegally in Britain.

Challenges by refugee charities in the courts had already reduced those scheduled to fly to a handful from more than 100, while the plan had already drawn sharp criticism from religious leaders including Archbishop of Canterbury Justin Welby, and Prince Charles, the heir to the throne.

The ECHR said the man due for deportation "should not be removed to Rwanda until three weeks after the delivery of the final domestic decision in his ongoing judicial review proceedings".'

It said it was granting the request on an "exceptional basis" because of "a real risk of irreversible harm".

"I know the public will be surprised that we have European judges overruling British judges," Cabinet minister Therese Coffey told Sky News on Wednesday (June 15).

The court is part of the Council of Europe - which still counts Britain as a member - rather than the European Union, which Britain left.

Britain played a role in drafting the convention after World War II, and it was enshrined in British law in the 1998 Human Rights Act.

Mr Johnson on Tuesday raised the possibility of pulling the UK out of the convention.

Speaking before the late rulings, he told broadcasters "the legal world is very good at picking up ways of trying to stop the government from upholding what we think is a sensible law".

Asked if it's time for the UK to come out of the convention, Mr Johnson said: "Will it be necessary to change some laws to help us as we go along? It may very well be, and all these options are under constant review."

The view that Britain should pull out of the convention is not universal among Tories.

Pensions minister Guy Opperman said he didn't advocate withdrawal.

"As I understand it, the UK courts have primacy on this matter," he told Times radio. "But as I understand the decision last night from the ECHR, a decision was made that not everything had been considered by the UK courts in those circumstances. This is a temporary delay."

Home Secretary Priti Patel called the ECHR intervention a surprise and vowed to push on with the policy, despite the setback.

"I have always said this policy will not be easy to deliver and am disappointed that legal challenge and last-minute claims have meant the flight was unable to depart," she said in a statement.

"These repeated legal barriers are similar to those we experience with other removals flights and many of those removed from this flight will be placed on the next."

The UK government argues that sending migrants to Rwanda will halt the flow of people arriving in small boats organized by people smugglers, often in treacherous conditions and with sometimes tragic consequences.