A so-called “People’s Vote” on Brexit could not be held within the next year, a government briefing document shared with opposition MPs claims. 

Ministers ordered civil servants to compile the paper for talks Theresa May is holding with opposition MPs who back the idea, after her bid to get her draft EU exit deal through the Commons failed this week.

It says legislating for and organising a second referendum would take “in excess of a year”. 

But the Electoral Commission, the independent body which regulates elections, said the government had not yet approached them. 

A spokesman said: “The Government has not provided us with any information about how long, in its view, it would take to organise a second referendum. We would expect to see any such information so that we can provide independent, expert advice.”

The prime minister is holding cross-party talks on what to do next about Brexit following her crushing parliamentary defeat on Wednesday. 

The single sheet of paper explores the timescale of a second poll, but does not propose what the question would be on the ballot paper, it was said. 

Number 10 insisted the paper shown to MPs was for “illustrative” purposes only and stressed the PM does not support the ideas set out within it.

“In order to inform the discussions a very short paper set out in factual detail the number of months that would be required,” May’s official spokeswoman said. 

“This was illustrative only and our position is that there will be no second referendum, as the PM has repeatedly said.”  

Supporters of a fresh vote, however, say a second poll could be held in a matter of months.

Former education secretary Justine Greening said if Article 50 were to be extended – effectively delaying the UK’s exit from the EU – a poll could be organised and legislated for within 22 weeks. 

In a speech in November, Greening named May 30 as a possible date. 

Former attorney general Dominic Grieve rejected the timetable as “simply wrong”.

“It is neither helpful nor right to have misleading information of this kind put out,” he said. 

Labour MPs Hilary Benn and Yvette Cooper, as well as Plaid Cymru’s Liz Savile-Roberts, Green MP Caroline Lucas and the SNP’s Ian Blackford were among the politicians set to meet May, or her cabinet ministers Michael Gove or David Lidington, on Thursday. 

All parties have been calling on the government to extend the current March 29 Article 50 deadline and take the prospect of a no-deal Brexit off the table. 

“The government knows as well as anybody else the damage that would be caused by no deal so why continue to pretend that they might be prepared to take the UK out of the EU on March 29 without an agreement?” said Benn, chair of the Brexit select committee.

“The essential first step is for the government to say ‘we will not do that because it’s in nobody’s interest for that to happen’.”

The prime minister has shown little sign she will budge, but has cancelled her scheduled visit to the World Economic Forum meeting in Davos next week to continue with crunch talks. 

News of the briefing document came as both May and Jeremy Corbyn were under increasing pressure to pivot and back a second referendum as another week of political turmoil was set to end without agreement. 

Labour wants a permanent customs union, close links to the single market and protections for workers and the environment, but has not ruled out a second referendum.

At a speech in Hastings on Thursday, he called for the option of no-deal to be taken off the table, saying: “If the government remains intransigent, if support for Labour’s alternative is blocked for party advantage and the country is facing the potential disaster of no-deal, our duty will then be to look at other options which we set out in our confidence motion, including that of a public vote.”

The official People’s Vote campaign also revealed it raised more than £100,000 in the 20 hours following May’s Brexit deal defeat on Wednesday. 

Tory MP Sarah Wollaston will put down an amendment to a government motion on Monday which could give MPs the chance to vote on a second Brexit referendum on January 29. 

Many backbench MPs remain divided, however. 

Former Tory minister Nick Boles and Labour’s Stephen Kinnock, meanwhile, are spearheading a cross-party bid to get MPs to support a Norway-style soft Brexit. 

 “The meetings have been focused on finding consensus and common ground to move forward in a way that can secure the backing of the House,” the PM’s spokeswoman added.