Boris Johnson expects negotiating a post-Brexit trade deal with the US will be a "tough old haggle" but he expressed confidence that Britain "will get there".

The Prime Minister's remarks came after John Bolton, Donald Trump's key aide on security, who met Mr Johnson and other senior ministers in London on Monday, said the UK would be "first in line" for a deal with the US, possibly on a gradual "sector-by-sector" basis.

The PM, speaking during a visit to Leeds, said he wanted to see increased trade with countries around the world and with Europe post Brexit.

"We have fantastic opportunities to open that up. Actually, the US market is growing very fast for the UK but they still ban haggis, for heaven's sake,” he declared.

While Mr Johnson stressed there were “all sorts of opportunities” on trade in the US and around the world, the single biggest deal Britain needed was one “with our friends and partners over the Channel".

"In my experience, the Americans are very tough negotiators indeed and we will do a great deal with them and it will open up opportunities for UK business, particularly service companies in the US but it will be a tough old haggle. But we will get there," he added.

However, Naomi Smith, head of the pro-EU Best for Britain, warned: "Britain won’t get a trade deal with the US if we rip up our treaty obligations and put the Good Friday Agreement in danger. Democrats and Republicans will block anything that damages Ireland so badly.”

She insisted Britain would be “far better off” as part of the EU single market, the world’s largest, where it would have far more clout in trade negotiations than on its own.

"We need to stop Brexit so we can focus on retaining the benefits of our EU membership,” added Ms Smith.

The Green MP Caroline Lucas also issued a warning, saying Messrs Trump and Bolton were “not behaving like friends, they’re circling like vultures”.

Meanwhile, the SNP claimed a “Tory-Trump trade deal” could seriously threaten Scotland’s NHS and future prosperity, saying it was too high a price to pay to placate the US President.

Emma Harper, the SNP MSP, stressed how the Conservative Government wanted to “rip us out of the world’s largest single market under the illusion they can win fantastic trade deals with the US and a long queue of others”.

She warned an “extreme Tory Brexit” would completely undermine the Scottish Government’s efforts to boost Scotland’s trading position and seriously threaten the nation’s international reputation.

“The UK Government simply must not be allowed to negotiate away the rights of Scottish food producers, our exporters, and our NHS,” added Ms Harper.

In his first Commons appearance after becoming PM in July, Mr Johnson insisted: “Under no circumstances would we agree to…any free trade deal that put the NHS on the table. It is not for sale.”

In other developments:

Amber Rudd, the pro-Remain Work and Pensions Secretary, denied she was a "sell-out" after changing tack, saying she believed the risks of a no-deal Brexit were no more than a challenge that could be countered by UK Government action, a shift from her previous assessment that it would cause “generational damage” to Britain;

*Next chief Lord Wolfson said the worst outcome of a no-deal Brexit would be "mild disruption" given the Government’s preparations, stressing how UK ministers were now taking leaving the EU seriously;

*young activists from the pro-EU campaign group Our Future, Our Choice gathered outside the Scottish Tory HQ in Edinburgh to warn against the threat of no-deal Bx to the Union as they donned masks representing key Brexiteers such as Mr Johnson, Michael Gove and Jacob Rees-Mogg and unfurled a banner, saying: "No Deal = No UK" and

*anti-Brexit campaign group Led By Donkeys posted adverts on billboards across the UK, showing previous no-deal Brexit warnings issued by Government ministers such as Mr Gove and his Cabinet colleague Nicky Morgan.