Boris Johnson’s Government is “planning to throw” Scottish farmers and crofters “under the Brexit bus” over trade negotiations with Australia, SNP Westminster leader Ian Blackford has claimed.

Mr Blackford warned “this deal would be the final nail in the coffin for many Scottish crofters and farmers” as he called on Mr Johnson to “ditch a deal that will send our farmers down under”.

The Prime Minister hit back, accusing Mr Blackford of “grossly underestimating” the ability of the farming industry to “make the most of free trade”, adding: “Why is he so frightened of free trade?”

Speaking during PMQs Mr Blackford said: “The UK Government led the betrayal of Scottish fishing and now the Tories are planning to throw our farmers and crofters under the Brexit bus.”

He added: “This deal would be the final nail in the coffin for many Scottish crofters and farmers, it will end a way of life that has endured for generations, Prime Minister.

“I know that many of the Prime Minister’s Tory colleagues privately agree with me and want him to pull back from this deal.

“So will the Prime Minister finally listen, think again and ditch a deal that will send our farmers down under?”

Responding, Mr Johnson said: “First of all he’s totally wrong about what he says about the fisheries because in fact there are massive opportunities for fisheries for the whole of the UK as we take back control of our territorial waters.”

He added: “He is grossly underestimating the ability of the people of this country, the agricultural communities of this country, the farming industry to make the most of free trade.

“This is a country that grew successful and prosperous on free trade on exporting around the world.

“Our food exports are second to none, he should be proud of that, we should be celebrating that and all he does is call for us to pull up the drawbridge and go back into the EU to be run by Brussels, that’s his manifesto and I think the people of this country have decisively rejected it.”

Mr Blackford called on the Prime Minister to “categorically rule out that his Government is prepared to sign up to a trade deal that will at any future point guarantee tariff-free access to Australian lamb and beef”.

He said: “As a member of Scotland’s crofter community I understand just how disastrous the Brexit trade deal with Australia as proposed by this Tory Government would be for Scotland’s farming and crofting sectors.

“If reports of this Tory deal are true, farmers will lose their livelihoods, rural businesses will collapse and ultimately families will be driven off the land and let’s be very clear if that happens this UK Tory Government will be solely responsible.”

Mr Johnson drew laughter from the Tory benches as he said: “I’m delighted to see the shots of his croft by the way, a humble representative of the crofting community.”

He added: “I don’t think that he does justice to crofters, to farmers across the country and in Scotland as well because I think he grossly underestimates their ability to do great things with our free-trade deals, to export Scottish beef around the world.

“Why doesn’t he believe in what the people of Scotland can do?

“Why is he so frightened of free trade?

“I think there’s a massive opportunity for Scotland and for the whole of the UK and he should seize it and be proud of it.”