(Bloomberg) -- The U.K. government’s push to send some asylum seekers to Rwanda may not deter enough migrants to make the effort cost effective, the Home Office official charged with assessing the plan said Saturday.

Migrants who cross the English Channel on small boats risk being relocated to the African state with a one-way ticket, Prime Minister Boris Johnson said Thursday in presenting the measure. His government will pay Rwanda about 120 million pounds ($158 million) to house them and process their asylum applications, Cabinet minister Simon Hart told Sky News. 

Boris Johnson Reveals Plan to Send Asylum Seekers to Rwanda (1)

Matthew Rycroft, the permanent secretary for the Home Office, said he led “a rigorous assessment of the regularity, propriety, feasibility and value for money of this policy.” Even if it proceeds, the plan could fail to reach its objectives of deterring immigration and reducing costs, he wrote in a letter to Home Secretary Priti Patel. The U.K. spends more than 1.5 billion pounds on its asylum system a year and 4.7 million pounds a day on hotels to house migrants. 

“Evidence of a deterrent effect is highly uncertain and cannot be quantified with sufficient certainty to provide me with the necessary level of assurance over value for money,” he wrote. “I do not believe sufficient evidence can be obtained to demonstrate that the policy will have a deterrent effect significant enough to make the policy value for money.”

About 28,000 people made the crossing last year -- it’s a journey that’s been been a regular source of tension with France, with the U.K. accusing President Emmanuel Macron’s government of not doing enough to prevent migrants leaving French shores.

By putting the emotive issue of immigration on top of the political agenda, Johnson is trying to rally support before next month’s local elections in England and Wales, with polls suggesting his Conservative party is set for significant losses.

Johnson championed the Brexit campaign, which was fueled by the promise that the U.K. would be able to clamp down on immigration once it left the European Union. Johnson’s failure to solve the issue since becoming prime minister in 2019 has been embarrassing for his administration, given his promise to “take back control” of Britain’s borders.

©2022 Bloomberg L.P.