Four months ago, Prime Minister Boris Johnson said the first navy ships would patrol the busy waterway and help to ensure that “no boat makes it to the UK undetected”.
Since then, the number of migrants reaching the UK's southern coast has risen to more than 20,000 and the government has announced the Rwanda deportation plan, in part to act as a deterrent for migrants using the dangerous Channel route.
Policing the English Channel has turned the hard-pressed navy into a “super taxi service” for migrants at a time when its ships are needed for other key military duties, MPs said.
The new prime minister, either Foreign Secretary Liz Truss or former chancellor Rishi Sunak, will have to decide whether to overrule military advisers.
Both Conservative leadership contenders have said the Channel migrant crisis would be a top priority if they secured the keys to Downing Street.
Despite the navy policing the Channel, the number of migrant crossings has already doubled this year.
However, Home Office officials are said to be concerned a sudden end to the navy’s role could send the wrong message to people smugglers.
“As planned, defence support to the Home Office will continue until January 2023, at which point the operational and wider arrangements will be reviewed," an MoD spokesperson told The National.
“We are working across government to ensure the conditions are set for defence to hand the task back to the Home Office following the review, this includes supporting training and capability development."
The MoD said the original idea had been for a January 31 end to the operation but it was also possible the plan could be reviewed.
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Last week it was announced that the ministry had sunk plans for an asylum camp at a base in North Yorkshire, a centrepiece of Home Secretary Priti Patel’s plans to reduce the £3 million ($3.6m) daily cost of housing migrants in hotels.
A day earlier, Mr Sunak, a local MP in North Yorkshire, had declared his opposition to it.
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The government gave the ministry £50m in April to take charge of the Channel migrant crisis.
An 80-metre offshore patrol vessel was to support Border Force interceptions, along with six fast training boats, three rigid-hulled inflatables and a Wildcat helicopter.
The vessels were first used in Operation Isotope as Mr Johnson unveiled plans to deport Channel migrants to Rwanda to claim asylum in the central African state and break the people-smugglers’ business.
The navy would continue with the operation “until the deterrent effect is achieved and the cross-Channel route for small boats collapses”, James Heappey, the Armed Forces Minister, told MPs in January.
The navy’s main role has been to co-ordinate Border Force and coastguard vessels at sea to rescue migrants and take them ashore, with sailors quayside to shepherd people to migrant-processing centres.
But senior MPs and Border Force officials say that the operation failed to stem the flow of migrants and distracted navy resources from other duties at a time of heightened tension with Russia.
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Tobias Ellwood, chairman of the House of Commons defence committee, told the Telegraph it was a “folly project” by Downing Street to distract from the issue that attempts to stem the flow of migrants across the Channel had failed.
John Spellar, a former Labour armed forces minister, said: “There was never any clear rationale as to what role they would do.
"They ended up providing a super taxi service that they had to do under centuries-old laws of the sea to save lives. It was an utterly flawed intervention."