Rwanda said the U.N. refugee agency had lied when the organisation told a British court this week that asylum seekers sent to the East African country could be moved on again to states where they risked torture or death.

Lawyers representing the United Nations High Commissioner for Refugees (UNHCR) told the court on Monday that Rwanda's asylum system was inadequate, as part of a challenge to the British government's policy to deport asylum seekers there.

The lawyers said removing asylum seekers to Rwanda put them at risk of being transferred again in a banned process known as refoulement - building on past evidence which formed an important part of the UK Supreme Court's reasoning when it ruled last year that the British plan was unlawful.

"UNHCR is lying," Rwanda's government spokesperson said in a statement late on Tuesday.

"The organisation seems intent on presenting fabricated allegations to U.K. courts about Rwanda's treatment of asylum seekers, while still partnering with us to bring African migrants from Libya to safety in Rwanda," the spokesperson added.

A UNHCR spokesperson in Rwanda said she had no immediate comment.

Rwanda's government said cases raised by the UNHCR lawyers in court had involved people arriving in Rwanda who had legal status in other countries but did not meet entry requirements, or of people leaving Rwanda voluntarily.

Britain said last week that the first flight to Rwanda would take off on July 24, though that was dependent on Prime Minister Rishi Sunak Conservatives winning national elections on July 4.

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