LONDON: The cost to UK authorities of detaining and deporting people over the next two years under the country’s controversial new Illegal Migration Bill could reach £6 billion ($7.5 billion), according to internal government projections obtained by the BBC.

The bill, passed by the House of Commons in April, includes mechanisms designed to make it easier to detain people who enter the UK illegally, particularly those who cross the English Channel on small boats, and send them back to their home countries or third-party nations.

The Conservative government has not revealed the projected costs associated with the legislation. However, the BBC reported on Monday that the Home Office estimates it will have to spend between £3 billion and £6 billion on detention facilities, accommodation and deportations.

Home Office sources said the bill will be costly and complex, with one insider admitting that implementing it will be a “major logistical challenge.” A senior government source told the BBC the bill could constrain public spending.

Home Office officials hope the legislation will act as a deterrent and that as the number of people being detained falls over time, so too will the costs. The Treasury is publicly supporting the policy but insiders are said to be concerned that the deterrence aspect has not been sufficiently proven. One Home Office source close to the bill described this deterrence effect as an “unknown factor” that cannot be predicted.

Jon Featonby, chief policy analyst at the Refugee Council, told the BBC: “The Home Office is clearly aware that so-called deterrence measures simply don’t work, and it is preparing to detain thousands of desperate people who will end up on our shores in search of protection.

“Until refugees fleeing violence and persecution are given a safe pathway to seek asylum in our country, they will continue to risk their lives to get here.

“Instead of moving forward with this hugely expensive and unworkable crackdown on refugees seeking safety in the UK, the government should be focusing on creating a system that protects the right to claim asylum and that prioritizes both compassion and control.”

Rob McNeil, the deputy director of Oxford University’s Migration Observatory, told the BBC that the big question is whether the bill will deter anyone from trying to enter in the UK. He pointed out that the costs are already “very, very high,” and said that if asylum claims were processed quicker, there would be fewer migrants in the system.

Yvette Cooper, the opposition Labour Party’s shadow home secretary, told the BBC: “The Conservatives are in total chaos on asylum and their new bill is a sham that will make the soaring costs far worse.”

The bill has faced a backlash within the ruling Conservative Party and in the House of Lords, where it is currently being debated. The government said it will release its economic impact assessment of the bill in due course.