UK Prime Minister Rishi Sunak said on Thursday he was open to toughening up his controversial plan to send migrants to Rwanda, which has divided his ruling Conservative party.

The plan is Sunak's answer to a unanimous Supreme Court ruling last month that deporting asylum seekers to Rwanda is illegal under international law.

Sunak, who has been in power for just over a year, has staked his political future on cutting record levels of regular and irregular migration, with the issue set to be a key battle ground in the next general election.

The British leader faced down party rebels earlier this week by winning a knife-edge parliamentary vote on the so-called Safety of Rwanda (Asylum and Immigration) Bill.

But he faces having to make concessions in the new year to Tory right-wingers, who want the bill toughened up, all while having to please moderates n the party, who insist the legislation already goes far enough.

"I've been very consistently clear, as have all ministers. If there are ways that the legislation can be improved, to be made even more effective -- with a respectable legal argument and maintaining the participation of the Rwandans in the scheme -- of course we would be open to that. Who wouldn't be?" Sunak told reporters.

- Disregarding UK and international law -

The emergency bill, published just last week, is Sunak's answer to the Supreme Court decision that the flagship policy was unlawful.

It would compel judges to treat Rwanda as a safe third country and proposes giving UK ministers powers to disregard sections of international and British human rights legislation.

The bill has triggered deep factional Tory infighting not seen since wrangling over what form Brexit should take.

The feuding threatens to weaken Sunak's authority going into a general election expected next year, which the opposition Labour Party is currently expected to win.

"We are confident this is a very strong piece of legislation. I think most legal experts, former judges have all said that the legislation is incredibly strong, it is effective, it will work," Sunak added.

"The key now is to get it on the statute books so we can get the scheme up and running," Sunak said.

The plan -- which would see would-be refugees who arrive in the UK via unauthorised routes deported to the African country -- is a key part of Sunak's pledge to "stop the boats".

Almost 30,000 asylum seekers have crossed the English Channel from northern France on rudimentary vessels this year.