Rwanda's asylum system is still inadequate, the United Nations refugee agency said on Monday as it was given permission to intervene in London High Court challenges over Britain's policy to deport asylum seekers to the east African country.

Lawyers representing the United Nations High Commissioner for Refugees (UNHCR) say removing asylum seekers to Rwanda puts them at risk of being sent to another country where they face potential death or torture, known as refoulement.

The agency's evidence formed an important part of the UK Supreme Court's reasoning when it ruled last year that the plan was unlawful because of the risk of refoulement.

British Prime Minister Rishi Sunak in response to that ruling signed a new treaty with Rwanda and pushed new legislation through parliament, declaring that Rwanda must be treated as a safe country.

UNCHR lawyer Laura Dubinsky said, however, that there was evidence of continuing refoulement in Rwanda, including this year.

She added that British officials were told by UNHCR officials last year of "at least seven cases of refoulement" in 2023 at a meeting in Kigali on Dec. 7, the same day Sunak introduced Britain's new Rwanda law into parliament.

Government lawyers said in court documents on Monday that the new Rwanda legislation meant "removals to Rwanda should not have to await a final determination by the courts of the general safety of Rwanda".

The Rwandan government was not immediately available for comment.

Britain said last week that the first flight to Rwanda would take off on July 24, though that is dependent on Sunak's Conservatives winning the national election on July 4.

That looks unlikely as the opposition Labour Party, leading by about 20 points in opinion polls, has pledged to scrap the plan if elected.