Sir Vince Cable has accused Boris Johnson of being a “Poundland Donald Trump” as the backlash against the Foreign Secretary’s 4000-word Brexit article continues.

The Liberal Democrat leader, demanded that Theresa May slap down Mr Johnson after he penned a provocative piece for The Telegraph in which he laid out a detailed plan for Brexit, just six days before the Prime Minister is expected to announce her own vision for Britain once it leaves the EU.

The article exposed a number of notable differences between the Foreign Secretary and other senior Cabinet ministers, including Chancellor Philip Hammond.

Mr Johnson was criticised for the article, which strayed beyond his ministerial remit, covering issues ranging from tax reform to housing policy.

Published the day after a terrorist attack at Parsons Green Tube station injured 30 people, it has been widely interpreted as a renewal of Mr Johnson’s long-held prime ministerial ambitions.

Ms May is set to deliver a major speech in Florence, Italy, next week where she will lay out her vision for post-Brexit Britain.

Speaking as he arrived in Bournemouth for the Lib Dems’ annual conference, Mr Cable said: “Boris Johnson is on manoeuvres, which means everyone else should take cover.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

“He clearly thinks that Theresa May is on the verge of a U-turn which would lead to atransitional deal that would keep us in the single market. Boris Johnson sees this as his chance to bag the top job, so is pushing for a far more extreme Brexit. This might play well with hard right Conservative MPs but would be a disaster for the UK economy.

“Theresa May must slap down Boris Johnson in the strongest terms or she will lose the last vestige of her authority to negotiate Brexit. The cabinet is more split than an oak tree struck by lightning. Britain desperately needs political grown-ups who will put the country first, not a Poundland Donald Trump like Boris Johnson.”

In his article, Mr Johnson said any attempt by the UK to remain in the EU single market and customs union would make a “complete mockery” of the referendum result.

Boris Johnson says the sums the EU are demanding for Brexit are extortionate

Britain should not pay for access to European markets but instead cut taxes in order to attract investment, he said.

The Foreign Secretary also repeated the contentious claim that the UK could invest an additional £350m a week in the NHS once it leaves the EU.

The timing of the article prompted criticism, including from within Mr Johnson’s own party.

In a thinly-veiled attack, Ruth Davidson, the leader of the Scottish Conservatives, wrote on Twitter: “On the day of a terror attack where Britons were maimed, just hours after the threat level is raised, our only thoughts should be on service."

However, a number of pro-Brexit MPs welcomed Mr Johnson’s intervention.

​Conor Burns, his parliamentary aide, wrote on Twitter: "Absolutely brilliant article in The Telegraph by Boris Johnson on our vision for Britain post Brexit. An optimistic and global future."

Crispin Blunt, the former chair of the House of Commons Foreign Affairs select committee, told the BBC’s Today programme: "His job as the great wordsmith of our present parliamentary party is to paint a picture of the future of the United Kingdom outside the European Union.