IAN Blackford, the SNP leader at Westminster, has warned Theresa May that she “can’t bludgeon on” with her Brexit strategy without seeking to take the Scottish Government with her.

The Nationalist MP’s words of caution came as Philip Hammond, the Chancellor, told his colleagues favouring a so-called “hard Brexit,” that it would be "madness" not to have the closest possible relationship with the European Union.

Opposition parties are already preparing to challenge the UK Government over its Repeal Bill, which is due to be published late next week. The bill will transpose all EU law into British law, enabling MPs to keep or discard what they want.

Sir Keir Starmer, the shadow Brexit secretary, said it was "highly likely" Labour would seek to amend the flagship legislation, Caroline Lucas, the Green Party co-leader, said she too was preparing to amend the bill while the SNP's Stephen Gethins made clear his party "had a responsibility" to work with others over the terms.

Already, the Prime Minister has indicated that a Legislative Consent Motion[LCM] from Holyrood on the bill will be needed so that Westminster can make law on issues normally devolved to the Scottish Parliament.

However, Michael Russell, the SNP administration’s Brexit minister, has made clear that while Holyrood would seek to be co-operative with Whitehall, it was “not a given” that MSPs would simply fall into line.

Any refusal by Holyrood to grant an LCM would spark a constitutional crisis and could threaten the UK Government’s tight legislative timetable; it aims to complete the process by March 2019.

In an interview with the FT, Mr Blackford said: “The Government needs to take a reality check…They cannot bludgeon on without seeking to take the devolved administrations with them.”

The Highland MP said he did not believe there was now a parliamentary majority for a hard Brexit.

Asked if anything short of single market membership would be acceptable, he replied: “We would have to see what was on the table. The best opportunity for us is very much to maintain membership of the single market.”

The issue of access to and membership of the single market as well as membership of the customs union is at the heart of the Brexit debate.

Mr Hammond, attending the G20 summit in Hamburg, called for an end to the "navel-gazing" that has dominated Westminster since the Conservative drubbing at the polls.

While he said he wanted a Brexit that recovered sovereignty for the UK, the EU would remain the country's largest trading partner.

"It would be madness not to seek to have the closest possible arrangement with them going forward," declared the Chancellor.

He went on: “I do not believe it is either legally or politically possible to stay in the customs union and in the single market.

"My preference is that we negotiate a transitional structure, which takes us outside of those memberships but in the transition phase replicates as much as possible of the existing arrangements so that the shock to business is minimised for the transition period."

Earlier at the summit, Theresa May stressed how Britain beyond Brexit wanted to ensure it could trade around the rest of the world.

“That means we can't be members of every part of the customs union. But we want to continue to have tariff-free and as frictionless trade across borders as possible because we want to ensure that we have that good trading relationship with the EU."

Her comments came 24 hours after Michel Barnier, the EU’s chief negotiator, said having frictionless trade outside the single market and customs union was impossible.

They also followed a speech by Carolyn Fairbairn, the CBI director general, who called for the UK to remain a member of the two bodies until a free trade deal with the remaining 27 member states was finalised.

Meanwhile, David Davis, the Brexit secretary, held talks with senior business figures at Chevening House, his grace-and-favour country residence in Kent.

The talks happened amid mounting frustration among businesses at the failure so far of ministers to spell out what arrangements will be put in place if there is no trade deal with the EU27 by the expected date of Britain's withdrawal in March 2019.

Afterwards, Terry Scuoler for the manufacturers' organisation EEF, said the meeting had been a “good first step” and ministers were listening to business concerns.

"We had an open and frank discussion and we've started a process where we will work together to obtain as much clarity and certainty as possible for industry as we prepare to leave the EU," he added.