The amendment going before the House of Commons consists of asking MPs to back the Withdrawal Agreement supported by the EU and Theresa May in return for a confirmatory referendum.
If Britain once again votes to leave the EU in a second referendum, it would do so on the basis of the Withdrawal Agreement which has twice been rejected by the Commons.
If the UK votes to remain, then the Withdrawal Agreement would not be needed.
Labour leader Jeremy Corbyn will reportedly support this. According to a Labour source, his message is that he does not support a referendum as a political choice but will support it as a last resort.
On Monday, May was frantically trying to win support for her deal on Tuesday with the DUP, the Northern Irish party, seen as critical to its chances of being approved.
If it is approved, the UK is then expected to ask the EU for a short extension - expected to be until the end of June - of the Article 50 process.
If it is rejected for a third time, however, that would most likely result in a much longer extension being required, possibly of at least one year. That would mean the UK would have to field candidates in the European elections in May.
“The proposal should appeal to all those MPs who want to take ‘no deal’ off the table because it makes the Withdrawal Agreement the new default. It also offers supporters of a People's Vote a public vote on the final deal” Roger Casale, New Europeans
The idea of agreeing on the Withdrawal Agreement in return for a public vote on it was first tabled by New Europeans, a Brussels-based group campaigning for the rights of citizens after the UK leaves the EU, but has been taken up by Labour MPs Peter Kyle and Phil Wilson.
It now seems that the two MPs are ready to table their amendment when Theresa May's Withdrawal agreement comes to the House of Commons for a third time on Tuesday.
Commenting on the proposal, Roger Casale, former Labour MP and founder of New Europeans, said, "What has attracted so much attention to the New Europeans’ compromise proposal is the fact that it offers a way to de-risk Brexit.”
“The proposal should appeal to all those MPs who want to take "no deal" off the table because it makes the Withdrawal Agreement the new default. It also offers supporters of a People's Vote a public vote on the final deal.”
“The only group this will not appeal to is the European Research Group. By calling for the Withdrawal Agreement to be passed, the proposal shoots the ERG's fox.”
Further comment came from political commentator, Ian Dunt, who, speaking of the compromise proposal, said, "This is a sensible attempt at a compromise: it turns the Withdrawal Agreement into the default Brexit and offers a democratic say on the final deal as it is in reality."
New Europeans has also called for the second referendum to be held on the day of the European elections in May.
Opinions differ on how long would be needed to organise a referendum, but Shadow Chancellor John McDonnell said, "The referendum could be organised in a "relatively curtailed period of time."
Key factors which will affect the timing include the time it takes for legislation to be passed through Parliament, the nature of the referendum question itself and whether or not the referendum was held on the same day as other elections.
All of these factors will, it is argued, be defined by the new referendum bill that would need to be laid before Parliament, subject to the procedural constraint that there should be a minimum 10-week period for the campaign.
The UCL Constitution Unit in the UK states, "Political considerations rather than procedural constraints are likely to dictate the minimum time in which legislation could pass through Parliament."
Meanwhile, in response to reports of changes to the Attorney General’s legal advice on the Brexit Withdrawal Agreement, Shami Chakrabarti, the shadow Attorney General, said on Monday: “We know that faced with historic defeats in Parliament, Theresa May’s approach is to stubbornly keep going back for a different answer. But fingers in ears don’t change the law.”
“You can’t keep asking for different legal advice to save your political skin. The public needs to know if the Attorney General is being pressured to embroider his analysis and why any new words from him may have only been disclosed to a few chosen Tory MPs.”