Defence chiefs are considering a formal request from the Home Office for naval support to deal with migrants attempting to cross the English Channel in small boats.

The call for the Royal Navy to assist Border Force in the Dover Straits came as the Government faces increasing pressure to deal with record numbers of people trying to make the perilous journey.

Home Secretary Priti Patel vowed to make the route used by asylum seekers “unviable” but conceded there are “legislative, legal and operational barriers” to stopping the boats.

However, ministers were warned of potentially fatal capsizings and legal challenges after it emerged they were considering blocking boats in the Channel before they enter British waters.

The Ministry of Defence (MoD) said on Saturday that it is “working hard to identify how we can most effectively assist” after receiving a request under the military aid to the civilian authorities (MACA) protocol.

“As ever, the MoD will do all it can to support HMG requirements,” a statement said.

Assistance likely to be under consideration includes surveillance, reconnaissance and command control.

But the request came after an MoD source told the PA news agency that any request for naval assistance would be “completely potty”.

“We don’t resort to deploying armed forces to deal with political failings,” the source said.

The Coastguard dealt with a “number of incidents” off the Kent coast on Saturday, after the Home Office said 146 migrants made it to the UK in 17 boats on Friday.

On Thursday, at least 235 migrants made the dangerous journey in 17 boats, setting a new single-day record.

Immigration Minister Chris Philp said he will meet French counterparts next week to work “to stop these illegal migrants from getting in the water in the first place”.

But he also wrote in the Telegraph that “we need to intercept those who manage to leave France” and said he would encourage the French “to look hard at interceptions at sea”.

And Schools Minister Nick Gibb told BBC Radio 4’s Today programme that the UK will be using “boats to try and prevent people from leaving and from making that very dangerous crossing across the Channel”.

A Home Office source did not rule out reports that ministers are controversially considering the possibility that Navy and Border Force vessels could be used to block boats in the Channel.

“There are a number of operational decisions under consideration,” the source aid.

Labour former home secretary Jack Straw warned that any move modelled on Australia’s controversial “push-back” approach deployed against migrants from Indonesia could have deadly consequences.

“I don’t think that just trying to push these people back is going to work and it will only take one of these dinghies to capsize and everybody to drown, which is perfectly feasible, for their to be a hullabaloo, including in the Conservative Party, and for the policy to have to be reversed, so I wouldn’t go down that route,” he told Today.

“The crucial point here is the obvious one, is that it requires the co-operation of the French.”

Bella Sankey, director of the Detention Action human rights campaign, described the possibility of boats being forced back into French waters as “an unhinged proposal” which would be met with legal challenges.

She told the PA news agency: “It’s unlawful, it’s really dangerous and could seriously risk human life. From any way you look at it it’s a terrible idea, and I don’t think it would actually get off the ground.

“If they did try and go down the route of push-backs at sea, absolutely they would face legal challenges.”

Kent County Council leader Roger Gough said its services are facing “enormous” pressure in dealing with unaccompanied minors who are seeking asylum, with nearly 400 arriving this year, a figure already exceeding the whole of 2019. Sixty minors arrived in the first week of August, including 23 on Friday alone.

“We’ve not seen figures like that or anywhere near that since 2015 when we did have a very big crisis,” he said.

The greatest success seen in the past was brokering arrangements to tackle the situation with France, Mr Gough said when asked about the potential use of the Navy.

“That may be a way of dealing with it but I think, certainly historically, the best experience we’ve seen of reducing the inflows is when there’s been a successful agreement, level of shared interest, between the British and French authorities,” he said.