“At the beginning of these European election campaigns, we had time to provide for a People’s Vote on what happened on Brexit, which would take at least five to six months. We now no longer have the time to do that by 31 October”

That was the claim from the Change UK spokesperson, Chuka Umunna on yesterday’s Andrew Marr show.

It’s one of the reasons he believes “we are now at a point where we are going to need to revoke Article 50”, thereby cancelling Brexit.

Just minutes later, Lib Dem leader Vince Cable directly contradicted him, asserting that a “confirmatory referendum” “can be done before October”.

So who’s right?

How long does it take to arrange a referendum?

As it stands, we’re due to leave the EU on 31 October this year.

In order to hold a second referendum: parliament would have to pass legislation, the Electoral Commission and others would need to work out what question actually goes on the ballot, and the various camps would have to register with the Electoral Commission and get time to actually campaign.

The independent Institute for Government (IfG) think tank said last year that it would take at least 21 weeks to complete the process. Last October, the Constitution Unit at University College London (UCL) said we’d need a minimum of 22 weeks.

Change UK cited both the IfG and UCL reports when we asked them for the source of Mr Umunna’s claim. But on a strict interpretation of his words, they don’t support the claim he was making.

According to the timeline set out in the UCL report, the last day you could introduce legislation for a referendum and have time to get it done properly before 31 October is 23 May (this Thursday). According to the IfG, it’s 30 May.

In other words, we are extremely close to, but have not yet passed, the point after which a second referendum could not be called in time for our scheduled departure date.

We put this to Change UK, who told us: “It’s a question of semantics. We are not technically, strictly, legally past the point where we no longer have time – that is on Thursday (given the 22-week timetable).

“But it is 99.99 per cent certain that there will not be legislation introduced by Thursday. So in that sense we are past the point.”

Are there any other routes to a second referendum?

For argument’s sake, let’s take Change UK’s point that it’s extremely unlikely legislation will be brought to parliament in the next few days to trigger a second referendum by 31 October. Are there any remaining routes to a “people’s vote”?

Dr Alan Renwick, one of the authors of the UCL report, told us it would be possible in theory to ignore normal procedures and shorten the 21- or 22-week timetable, but that doing so would risk damaging the legitimacy of the second ballot.

He said: “If the referendum has the potential to overturn the result of the 2016 referendum, it would be dangerous to follow a process that is less robust than the one used in 2016 – whether, for example, that is by not testing the question properly or giving campaign groups less time to organise.”

The Electoral Commission told us that “any decision about whether a referendum takes place is a matter for government and for parliament. The Electoral Commission and the wider electoral community have experience of delivering polls at short notice.”

But they say they “have recommended that legislation should be in place six months before an referendum polling day. This would provide enough time for electoral administrators to plan and for campaigners to make their arguments to voters.”

If we can’t change the timetable of a second referendum, can we push the deadline back?

Dr Renwick said: “There is no very strong reason for rushing a referendum. If the UK decided by 31 October to hold a referendum, the EU27 would very likely grant a further extension to allow it to happen.”

He adds: “If a referendum were held in late October, a further extension would really be needed anyway, to give time for implementing a decision to leave. That would particularly be the case of ‘no deal’ was an option on the ballot paper.”

Deferring our departure date from the EU would require parliament to pass legislation and the EU to grant the extension.

FactCheck verdict

Change UK’s Chuka Umunna said yesterday that “we do not have time to do a people’s vote before 31 October”. This is one of the reasons he believes we should now revoke Article 50.

His party says that’s based on reports from the Institute for Government and the Constitution Unit at University College London, which calculate it would take at least 21 or 22 weeks to prepare for a second referendum.

But if those timetables are accurate, then Mr Umunna’s claim that we’re already out of time isn’t quite correct. By those calculations, the “deadline” for passing legislation would be Thursday 23 May or Thursday 30 May.

Change UK seemed to concede this point when we put it to them, accepting that “we are not technically, strictly, legally past the point where we no longer have time”. However, they said that “for all practical purposes” it’s too late to get legislation through parliament in the next few days.

That may well be true. In either case, there are other routes open to those who want a second referendum. The procedure for setting up the referendum could be shortened and/or the UK could seek a further extension to Article 50. Both have their drawbacks, but are by no means impossible.