LONDON   -  The UK readied on Tuesday to start detention of migrants within days before deporting them to Rwanda, after the controversial plan cleared its final hurdle, sparking criticism from the UN and rights groups. The new law -- a flagship policy of the Conservative government that wants to curb irregular migration -- finally got the green light after a marathon parliamentary tussle lasting late into Monday night.

Under the scheme, undocumented asylum seekers arriving in Britain would be sent to Rwanda, where their asylum claims would be examined and, if approved, would allow them to stay in Rwanda. Prime Minister Rishi Sunak says deportations are expected to begin within 10-12 weeks, with migrants identified for the first flight due to be detained and held from as early as this week. 

“Starting from the moment that the bill passes... we will begin the process of removing those identified for the first flight,” he told reporters earlier on Monday. “We have prepared for this moment to detain people while we prepare to remove them. We’ve increased detention spaces to 2,200.” Rwanda said it was “pleased” to see the bill passed and was looking forward to “welcoming those relocated to Rwanda”.

But the heads of the UN agencies for refugees and human rights warned it threatened the rule of law and set “a perilous precedent globally”. 

They urged the UK to instead “take practical measures to address irregular flows of refugees and migrants, based on international cooperation and respect for international human rights law”. The Council of Europe also called for the new law to be scrapped, with human rights commissioner Michael O’Flaherty saying it raised “major issues about the human rights of asylum seekers and the rule of law more generally”.