How could Britain hold a second Brexit referendum?

The centrist and pro-European Liberal Democrats, who have only 11 MPs in parliament, have been calling for a second referendum ever since the last one in 2016.

British Prime Minister Theresa May. Picture: AFP

LONDON, United Kingdom - The question of whether or not Britain should hold a second Brexit referendum has come to the fore despite Prime Minister Theresa May's staunch opposition.

Here is a summary of the main issues around this option:

WHO IS IT FOR?

The centrist and pro-European Liberal Democrats, who have only 11 MPs in parliament, have been calling for a second referendum ever since the last one in 2016.

The main opposition Labour Party has remained ambiguous on another poll but has not ruled it out, mindful that its voters include both supporters and opponents of EU membership.

Dozens of Labour MPs, however, do support it and are putting pressure on leader Jeremy Corbyn, a lifelong eurosceptic, to get behind it.

A few Conservative MPs also support a new public vote.

Former prime ministers Tony Blair and John Major have been particularly powerful advocates from the sidelines, while the so-called "People's Vote" campaign has been especially active.

WHO IS OPPOSED?

May is solidly opposed to a second referendum along with her cabinet, arguing that failure to respect the result of the 2016 referendum would undermine trust in politicians.

Many Conservative MPs are also opposed, including the same Brexiteers who plotted to oust May last week.

Northern Ireland's Democratic Unionist Party, whose 10 MPs provide the government with its working majority in parliament, is also strongly opposed to a vote.

Brexit firebrand Nigel Farage, former head of the UK Independence Party, is opposed but believes it will happen and has urged supporters to prepare for a campaign.

As with much of Brexit, the public are almost evenly split.

A poll of polls compiled by NatCen Social Research showed that 53% would vote to remain and 47% would vote to leave if the question is asked in a second vote.

WHO DECIDES ON HOLDING IT?

The government would have to give its go-ahead for a second referendum and parliament would have to vote by a majority in favour of holding one to approve the legal framework.

New primary legislation would be required to spell out details such as the question, the poll date and who would be allowed to vote. Some details, such as the date, can be determined later by a parliamentary directive.

WHAT WOULD BE THE QUESTION?

There is no agreement on this. Some supporters of a second referendum say the option of remaining in the EU should not be on the ballot as Britain has already voted on this.

That would mean voters decide between May's agreement and a so-called no-deal scenario.

Other supporters want a ballot on the prime minister's package and staying in the bloc, warning that presenting the option of no-deal could be dangerous because of the economic consequences of such a scenario.

Others support all three questions being on the ballot.

Voters could then be given a second vote which is counted if no option gets 50% or more for first preferences and their first choice is knocked out.

HOW LONG DOES IT TAKE TO HOLD ONE?

The timing is a particularly difficult conundrum.

The constitution unit of University College London has calculated that the shortest possible time between deciding to hold a referendum and holding one is around 22 weeks.

If a decision were to be taken on Monday, the referendum could, therefore, be held at the end of May at the earliest.

The two-year timetable for Brexit by 29 March 2019 would, therefore, have to be extended to hold a referendum -- something that EU officials have hinted could be possible.

The main challenge would be what to do about European Parliament elections which begin on May 23.

Would Britain elect MEPs then in case voters choose to stay in the EU? Could it hold the elections at a later date?