Media playback is unsupported on your device Media caption Oliver Letwin tells Radio 4's Today why the government should abandon plans to appeal the court ruling on Brexit

Theresa May should abandon an appeal against the court ruling that means MPs must vote on the UK leaving the EU, leading Conservatives say.

Sir Oliver Letwin, former head of the government's Brexit preparations, and two former law officers said the case should not go to the Supreme Court.

Instead, they want ministers to bring a bill to Parliament to start the process of Brexit as soon as possible.

The government said it would robustly defend its position at the appeal.

The MPs voiced their concerns after the Supreme Court decided on Friday that the Scottish and Welsh governments should have a say at the appeal hearing in December.

Former minister Sir Oliver, who oversaw a "Brexit Unit" in the Cabinet Office after the referendum, told BBC Radio 4's Today Programme that the Supreme Court hearing could see ministers' powers outside Parliament curbed.

He added that one of the advantages of bringing a "fast and tightly timetabled and constrained bill" to Parliament, giving the government the ability to trigger Brexit without any constraints on its negotiating power, was that it avoided "any risk of the Supreme Court deciding to accord the devolved administrations some rights or even some veto powers" over triggering Article 50.

Image copyright Reuters Image caption The government is appealing against a High Court ruling in a case led by Gina Miller

Former Solicitor General Sir Edward Garnier said Mrs May should drop the appeal to avoid expense and a row about judges' powers, while former Attorney General Dominic Grieve said he could not see the point of continuing with the case.

All three said ministers should bring a bill allowing the government to begin leaving the European Union - triggering Article 50 - as soon as possible.

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Sir Edward said: "That way you avoid an unnecessary legal row, you avoid a lot of unnecessary expense, but you also avoid an opportunity for ill-motivated people to attack the judiciary, to misconstrue the motives of both parties to the lawsuit, and you provide certainty."

Mr Grieve said: "I can't see the point in the government continuing with the case and also agree that if they enact primary legislation, they will get it through Parliament.

"I think their chances of success in court are low."

Image copyright PA, Getty Images Image caption Sir Oliver Letwin (L), Sir Edward Garnier (C) and Dominic Grieve all support triggering Article 50 before the end of March

The three MPs all backed the Remain campaign at the June referendum. They all now support triggering Article 50 before the end of March - the deadline set out by the prime minister.

Conservative MP Owen Paterson, who was a Leave campaigner, said he believed the government had a "very strong case" for its appeal.

"The problem with getting into any saga with courts is you can't predict the outcome," he said, adding that uncertainty over Brexit was damaging for the economy.

"My concern is that we deliver on what the people wanted.... There was this huge vote to leave, it has to be delivered. If it is not delivered there will be the most shattering damage to the integrity of the establishment."

'On track'

A government spokesman said: "The country voted to leave the European Union in a referendum approved by an Act of Parliament and the government is determined to respect that result.

"We will robustly defend our position in the forthcoming appeal. As the prime minister made clear [on Friday], our work is on track and we remain committed to triggering Article 50 by the end of March next year."

The High Court ruled in early November that Parliament must vote on whether Article 50 could be invoked.

A final judgement from the Supreme Court is not expected until January.