The Daily Telegraph reported that officials and lawyers believe the court in Strasbourg could issue temporary injunctions, as it did to ground Tuesday’s flight, to stop asylum seekers from being deported to the East African nation.
However, the British government has vowed to stick with the policy despite growing fury in the Conservative Party over the decision made by the European Court for Human Rights.
Last-minute appeals were considered by an out-of-hours judge on papers that overruled UK rulings.
On Wednesday, some MPs threatened to withdraw Britain from the institution.
The immediate problem for Downing Street is surmounting the many legal challenges the Rwanda policy faces while countering allegations of incompetence.
Home Secretary Priti Patel said the government “will not accept that we have no right to control our borders” and “do everything necessary to keep this country safe and we will continue our long and proud tradition of helping those in genuine need”.
Speaking to MPs in the House of Commons on Wednesday, she said she would “not be deterred from doing the right thing”, adding: “Preparations for our future flights and the next flights have already begun.”
“While this decision by the Strasbourg court to intervene was disappointing and surprising given the repeated and considered judgements to the contrary in our domestic courts, we remain committed to this policy.”
She said the “opaque nature” of the court's decision is “concerning”.
UK minister says Britain will push ahead with migrant deportations to Rwanda — video
Shadow home secretary Yvette Cooper branded the Rwanda policy “government by gimmick” and a “shambles that is putting our country to shame”.
The Rwanda deportations have been introduced in a £120 million ($150m) deal to deter the thousands of illegal immigrants who cross the English Channel on small boats. So far, 10,500 have crossed over this year, according to the latest figures, and more than 400 were rescued and brought ashore on Tuesday alone after attempting to cross the Channel to the UK.
The policy is to send asylum seekers to the central African country on a one-way ticket where the local authorities will assess claims with the potential to remain in Rwanda.
The law is particularly popular among voters in northern England where the Conservatives are anxious to retain “Red Wall” seats they won from Labour in the last election.
UK's first Rwanda deportation flight cancelled — video
After months of delays, the first flight was announced two weeks ago, with 130 asylum seekers set to board. Following legal challenges in the British courts up to Tuesday evening this was whittled down to seven, nearly all from Iraq or Iran.
An Iraqi citizen was the first to be successful in his appeal to the ECHR at 6.25pm, with the judge overruling three of the highest courts in the Britain.
Shortly before midnight in Strasbourg, the court, which is entirely separate from the European Union, upheld the appeals against the departure orders and the last six migrants disembarked from the chartered Boeing 767.
A High Court judicial review verdict of the Rwanda policy is expected at the end of July.
Prime Minister Boris Johnson implied that Britain would consider a drastic alteration in the law to override the ECHR, stating “it may very well be” a necessary change and all “options are under constant review”.
Hours before the decision, Mr Johnson suggested lawyers representing migrants were “abetting the work of criminal gangs” as last-ditch court hearings took place.
Following Second World War atrocities, Britain played a key role in creating the 1950 European Convention on Human Rights, that protects political and personal freedoms.
Mr Johnson's reaction reflects fury among Conservative immigration hardliners. “Outrageous that the UK is still beholden to the ECHR as a sovereign nation,” said James Sutherland, MP.
A government source rued that although domestic courts had allowed the removals “some foreign court has decided ‘no you can’t’”.
Some MPs are now demanding the UK withdraw from the European Convention on Human Rights which the ECHR oversees.
Rwanda prepares for refugees — video
Tory MP Jonathan Gullis said many of his constituents would be frustrated the flight was not able to take place. “The ECHR's role in UK law needs looking at urgently,” he posted on Facebook.
But a more restrained argument was made on Wednesday morning by Therese Coffey, the Work and Pensions Secretary, who said the government would pursue the case “through the appropriate legal routes” and that ditching the ECHR was not “on the table at all”.
The Home Office will now book another Rwanda flight, as Ms Patel vowed that the migrants removed from Tuesday’s aircraft “will be placed on the next”.
The decision was only a “temporary setback”, another government minister said.
Work and Pensions Minister Guy Opperman said he did not believe the ruling was “terminal” for the government’s policy.
“As I understand the decision last night, this is a temporary stay of the flight and the people going on the flight for there to be greater consideration of the individual circumstances of the situation by the UK courts,” he told LBC radio.
“It is not ‘You cannot do this’. It is a temporary stay that will then be considered by the UK courts on an continuing basis. I don’t believe that it is terminal judgment to the government’s cause.”
Afghan migrant documents dangerous journey across Channel — video
Rwandan government spokeswoman Yolande Makolo said: “We are not deterred by these developments.
“Rwanda remains fully committed to making this partnership work. The current situation of people making dangerous journeys cannot continue as it is causing untold suffering to so many.
“Rwanda stands ready to receive the migrants when they do arrive and offer them safety and opportunity in our country.”
Migration Watch UK, which campaigns for lower immigration into the UK, said the “absurd” ECHR decision “gives licence to continued asylum abuse”.
Frances Swaine, who represents a man due to be flown to Rwanda, told BBC Breakfast that the government should consider whether it is worth it “financially or legally” to attempt another flight.
She said: “The European Court of Human Rights has recommended that there are no other flights proposals put together until the substantial judicial review hearing into the whole policy is heard,” she said. “We’re expecting that that would take place in about six weeks’ time, during July, although we don’t have a firm date for it yet.
“And I think if I was the government, which obviously I’m not, but if I was, I would be sitting back and thinking was it worth it, either from a financial or a legal perspective, to organise one of these very expensive flights again when they’ve been so unsuccessful this time around on legal grounds.
“Because there will be a decision in July as to whether or not this policy can be extant, or whether there would need to be some changes to the law if the government was absolutely determined to see it through.
“But wait until we have the decision first and then decide whether to go ahead.”
She said she “understands” the frustrations of those who wanted the flight to go ahead.
However, she added that she hopes people frustrated over the flight would not want to do something that was illegal.