Rishi Sunak could learn by the end of the year whether a key plank of his “stop the boats” strategy has failed after the conclusion of a three-day Supreme Court hearing.

The court president Lord Reed suggested he and other four justices would take around two months to decide if the plan to send asylum seekers from the UK to Rwanda is lawful.

The Home Office has challenged a Court of Appeal ruling from June that the £120million deal with the east African state violates the law because of human rights concerns.  

The deterrent policy, which has yet to send one person to Rwanda, is seen as pivotal to the Prime Minister’s pledge to crack down on migrants making illegal Channel crossings.

At the conclusion of the hearing, Lord Reed said the ruling would be at a later date.

He said: “I appreciate that people will be anxious to know how long it will take to produce a judgment … I am hoping it will be a similar sort of timeframe to the lower courts.”

Both the Court of Appeal and High Court gave judgments on their respective cases around two months after the hearings ended.

The High Court initially ruled the scheme was lawful, but this was overturned by a majority decision at the Court of Appeal, a judgment Mr Sunak hopes will itself be overturned.

On Monday, Sir James Eadie KC, for the Home Office, told the UK’s highest court Rwanda was “a country less attractive” than the UK “but nevertheless safe” and the policy lawful.

The UK Government claims a memorandum of understanding agreed between the two countries provides assurances that ensure everyone sent there will have a “safe and effective” refugee status determination procedure.

Other assurances cover people deported to Rwanda receiving “adequate accommodation”, food, free medical assistance, education, language and professional development training.

But Raza Husain KC, acting for several asylum seekers facing deportation to Rwanda, said its asylum system was “woefully deficient … marked by acute unfairness and arbitrariness”.

The UNHCR, the UN Refugee Agency, also intervened in the Supreme Court hearing, with its barrister Angus McCullough KC telling the court the assurances were “no sufficient answer” to “basic and fundamental defects” in the Rwandan system.