A former Royal Navy chief has backed deploying warships to guard British fishing waters from European Union (EU) boats in case of a no-deal Brexit.
Retired Admiral Lord Alan West, a former First Sea Lord of the Royal Navy, told BBC Radio 4's Today programme that Prime Minister Boris Johnson's government was justified in its plan if last-ditch talks towards a post-Brexit trade deal fail - as looks likely.
The government would send four River-class armed Offshore Patrol Vessels, backed up by AgustaWestland Wildcat anti-shipping helicopters and a Merlin anti-submarine chopper to patrol the English Channel and Irish Sea against attempts by French boats to fish there illegally after the end of the post-Brexit transition period on 31 December.
"It is absolutely appropriate that the Royal Navy should protect our waters if the position is that we are a sovereign state and our Government has said we don't want other nations there", Lord West said.
But he pointed out that Parliament would have to vote to give captains authority to board, saying: "There are complications in that you can push vessels aside, you can cut their fishing tackle but boarding these foreign ships, they'll need to pass probably a little thing through Parliament to give authority to board and get on them".
And he said fishermen of all nations were "stormy people", so Royal Marine Commandoes might have to be sent aboard in case of a "punch-up".
"There is no doubt if you are a fisherman who has fished for years there - they are, as our fishermen are, quite stormy people - and you get a bit of a punch-up and you might need some Marines and things", the retired admiral told the BBC.
The patrol boats, named after major British rivers, measure 80 to 90 metres from bow to stern, with a displacement of 2,000 tons. The fastest of them can make 25 knots (46 kph) and they are armed with 30mm automatic cannon Gatling-style miniguns and general-purpose machine guns. Each boat can carry a contingent up to 50 marines, with two fast motorboats carried for intercepting small craft.
Remainers in the Conservative Party have attacked the gunboat threat. Former Hong Kong Governor and European Commissioner Lord Chris Patten said Johnson was acting like a "nationalist".
"While I hope for the best, I do fear for the worst because it is very, very difficult to see what the plan is, how we're going to do so brilliantly when we're out of this 'cage' of Europe - which we of course helped to build because the main constructor of the single market was Margaret Thatcher", Patten said.
Backbench MP Tobias Ellwood, chair of the House of Commons Defence Committee, called the move "irresponsible" and urged for more effort to strike a deal by Sunday.
"I think these headlines are absolutely irresponsible. We need to be focusing on what is already in the bag - 98 percent of the deal is there, there are three or four outstanding issues", he said, arguing they should be "parked" for future talks.
But both Johnson and European Commission President Ursula von der Leyen have warned there is little chance of resolving the key sticking points, which include EU demands for continued access to UK fishing waters after the extension period expires. Johnson said on Friday it was now "very, very likely" there would be no agreement.
But Polish-born Eurosceptic Tory MP Daniel Kawczynski demanded an "absolute guarantee" from the PM that the Navy would be sent to stop French boats fishing in British waters.
The Scottish devolved government's Justice Minister Humza Yousaf said "gunboat diplomacy" was not welcome there, insisting that civilian agencies Police Scotland and Marine Scotland - with three patrol boats - would protect the 62 percent of the UK's Exclusive Economic Zone that lies around Scotland, far from the likely area of dispute in the English Channel, Celtic Sea, and Irish Sea.
Yousaf's Scottish National Party (SNP) continues to oppose Brexit four years after the vote to leave, and has used the issue to demand a repeat of the failed 2014 Scottish independence referendum.
The opposition Labour Party's Mayor of Greater Manchester Andy Burnham called the gunboat threat "embarrassing".
— Andy Burnham (@AndyBurnhamGM) December 12, 2020
The threat of naval action is reminiscent of the "Cod Wars" between the UK and Iceland in the 1950s, 60s, and 70s. Ironically, Iceland's victory created the international norm of a 200-mile exclusive economic zone around each nation's coast, with EU member states now standing to lose access to the majority of the catch that they currently take.