SCOTTISH MPs have been urged to mount a cross-party defence of Britain’s membership of the European single market amid signs that the UK Government is uniting around a hard Brexit.

Chancellor Philip Hammond and International Trade Secretary Liam Fox put a summer of cabinet feuding behind them to declare that plans for post-Brexit transition period will not be a “back door” to continued EU membership.

Mr Hammond, who favours a “softer” pro-business Brexit, and Dr Fox, a hardline Brexiteer, signed a joint letter confirming that Brexit would mean leaving both the EU single market and the customs union.

They wrote: “We want our economy to remain strong and vibrant through this period of change. That means businesses need to have confidence that there will not be a cliff-edge when we leave the EU in just over 20 months’ time.

“That is why we believe a time-limited interim period will be important to further our national interest and give business greater certainty – but it cannot be indefinite; it cannot be a back door to staying in the EU.

“We are both clear that during this period the UK will be outside the customs union and will be a ‘third country’, not a party to EU treaties.”

SNP Europe spokesman Stephen Gethins said Scottish MPs “could hold the balance in ensuring Scotland’s place in the single market is protected”.

Ruth Davidson and Kezia Dugdale should remind themselves of what they said in the immediate aftermath of the EU referendum about fighting tooth and nail to ensure Scotland continues in the single market,” he said.

“They should have the courage of their convictions, show some leadership, and give their MPs at Westminster one clear objective – to put Scotland’s interests first.

“While the UK Government is consumed by the chaos of Brexit and deeply divided, Scottish MPs at Westminster can unite around a common objective of maintaining single market membership.”

Theresa May is running a minority government, meaning every vote will be crucial in delivering her Brexit ambitions.

However, any attempt to align Scottish Labour and Scottish Conservative MPs behind the single market would set them on a collision course with party leaders at Westminster.

Mrs May is firmly against the single market while Jeremy Corbyn sacked three members of his shadow cabinet for backing a soft Brexit in a recent parliament vote.

A Scottish Conservative spokesman said: “Scottish Conservative MPs will do what’s best for Scotland, not what’s best for the SNP.”

Scottish Labour’s Brexit spokesman Lewis Macdonald MSP said: “Despite today’s attempt to paper over the cracks, it is clear that Theresa May’s cabinet is deeply divided. Cabinet Ministers are more interested in positioning themselves to replace this lame duck Prime Minister and Tory leader, than delivering a Brexit deal that works for our country.

“The SNP claim to be interested in protecting our economy, yet their independence obsession would drag Scotland out of our largest single market - the UK - with which we do four times as much business with than the rest of the EU combined.

“A Labour government would deliver a jobs-first Brexit, with a deal that retains the benefits of the single market, protecting our jobs and industry.

“Only Labour can deliver an alternative to Theresa May’s race to the bottom Brexit.”