LORD Steel, the former Liberal leader, has urged Theresa May to make a television broadcast to call off Brexit.

The Liberal Democrat grandee urged her to accept the process was simply too difficult and damaging and that, she should halt it and call a People’s Vote.

The 80-year-old Scot claimed during a public broadcast she could cite the Governor of the Bank of England, the IMF, the UK car makers and even the Chairman of the John Lewis partnership in support not of “Project Fear but Project Reality”.

“I was active in the 1975 referendum but in this last one we heard little of the real reason for staying in the EU; namely, the need to maintain a highly successful international unit which has guaranteed that never again as twice in the 20th century would the nations of Europe be at destructive war.

“The PM should promise to work for reforms in the institution and to steer government investment to the underprivileged parts of England who, in desperation, voted out.”

He added: “In the words of the popular American song: let’s call the whole thing off.”

The former Holyrood Presiding Officer’s remarks came as campaigners for a second EU referendum set out a roadmap to obtain a "People's Vote" giving the public the final say on the outcome of Brexit negotiations.

The People's Vote report, written by Scottish peer Lord Kerr of Kinlochard, who authored Article 50, suggested the PM could be forced to concede a second referendum by a vote of MPs in Parliament or that she could even decide to call one herself.

And it insisted that the option of staying in the EU "must be on the ballot paper".

But Mrs May brushed aside the calls for a second referendum, saying voters had already made their decision.

"When the referendum took place, we gave people the opportunity to make a choice. They made that choice," she declared.

"This was probably the biggest exercise in democracy in our country's history. If we were to go back on that vote, it would destroy trust in politicians.

"My answer to the People's Vote is that we've had the people's vote - it was the referendum - and now we should deliver on it," she added.

The report argues that the March 29 2019 deadline for Brexit could easily be delayed to make time for a vote to be held.

And it warned that politicians would be judged harshly if they denied calls for a People's Vote on the grounds that it would be too difficult to arrange in the short time remaining.

"More than two years since the 2016 referendum, a political, economic and possibly constitutional crisis is gathering across the United Kingdom," said Lord Kerr, a former head of the diplomatic service.

"Our view is that the most viable and democratic way of resolving it is to allow the public to have their say on Brexit. To deny them a voice challenges the basic principle of informed consent."

And the crossbench peer warned: "History will not, in our opinion, be kind to any politician who hides behind purely logistical arguments, legalese or arcane parliamentary procedure in order to deny people a vote on the outcome of these Brexit negotiations at such a fragile and crucial moment for our country."

With opinion polls regularly finding a majority of voters now think the UK made the wrong decision to leave in 2016, the People's Vote report said it was not too late to "think again" about Brexit.

There was "no insurmountable political or procedural obstacle" to putting the two-year Article 50 process on hold to provide time for the necessary legislation and practical arrangements to be put in place for a vote, it argued.

And the report said a decision to dump Brexit now would be "cost-free" as the UK could retain its existing EU membership terms, including its budget rebate and exemption from joining the euro - while rejoining years later would require them to be renegotiated from scratch.

Drawn up by a cross-party committee including pro-EU MPs, peers and MEPs from Conservatives, Labour, Liberal Democrats and Greens, the roadmap outlined six possible routes to a fresh referendum but said others may emerge as events develop.

The report explained that if Mrs May secured a deal with Brussels this autumn, MPs could use parliamentary amendments to force a referendum either when voting on the deal itself or on later legislation to implement the withdrawal agreement.

If her deal were rejected by the Commons, it would be up to Speaker John Bercow to decide whether or not to permit MPs to vote on a fresh referendum when the PM faced Parliament to explain her next steps.

Although Mrs May has consistently said that she would not allow a second referendum, the report suggested she might decide that a public vote was the best way to win a mandate for her deal or to escape the "constitutional crisis" of no deal.

"Facing the very real possibility of overseeing a deeply unpopular and potentially disastrous no-deal Brexit, she may decide that the only way to avert this outcome is to put her deal to the public through a People's Vote," suggested the report.

The sixth option of a vote following victory for a pro-referendum party in a snap general election within the next few months was judged "very unlikely but not inconceivable".

The roadmap made no recommendation on the question to be asked in any poll, something that would ultimately be a matter for the independent Electoral Commission.

But it said that, for reasons of "simplicity, speed and clarity", it was likely that a two-way choice - either "the Government's deal versus stay" or "no deal versus stay" - would be preferred over a multiple choice question.

Any vote should not be delayed by arguments over whether to extend the franchise to include 16 and 17-year-olds and expats or tighten social media rules.

But the report said social media companies should be warned they would face tougher regulation in future if they failed to take all actions within their power to prevent abuse of their platforms by campaigns.

David Davis, the former Brexit Secretary, asked how likely a second referendum would be if Parliament willed it, replied: "Pretty unlikely because most people understand to announce a second referendum would be to invite the European Union to give us the worst deal possible in order to persuade us to stay in.

"That's the consequence of a second referendum and is why it's a very bad idea; it's completely against the national interest."