LONDON (Reuters) - A group of British lawmakers said on Tuesday they would try to force Prime Minister Theresa May to seek a delay to Britain’s departure from the European Union to prevent a chaotic no-deal exit on April 12.

A Union Jack flag flutters over the Houses of Parliament in London, Britain, April 2, 2019. REUTERS/Alkis Konstantinidis

The plan, which is outside the government’s control, relies on passing a piece of legislation that forces May to seek an unspecified delay to Brexit, but how would it work?

STEP ONE: Control the agenda

To pass legislation, the group of lawmakers pushing the plan need to secure time in parliament to debate and vote on it. The government usually has sole control over what is discussed in parliament.

But lawmakers have already voted to overturn that convention and the group behind the latest plan has so far used control of the agenda on two other occasions to hold votes on alternative Brexit options.

The Sun newspaper reported that the group had set out a proposed timetable to push the legislation through the Commons in a single day on Wednesday.

A photograph of the plan published on Twitter showed this would involve completing the final stages of the bill - a process likely to involve voting - by 2100 GMT. Votes at earlier stages of the legislation could also be held before then.

STEP TWO: Pass the legislation

New laws in Britain require the approval of both houses of parliament - the elected House of Commons, the main legislative body, and the unelected House of Lords, which is principally seen as a revising and refining mechanism, but does technically have the power to block laws.

The Commons requires legislation to pass through several stages of voting and revisions. This process can take months, but can also be compressed. Laws have previously passed through in a day when necessary.

The Lords has a similar multi-stage process, but unlike the Commons, there is no ability to time-limit or control the debate. Legislation usually passes through the Lords more slowly, but there is precedent for rapid approval.

Once approved by both Houses, the legislation requires Royal Assent - normally a formality - before it becomes law.

WHAT DOES THE LAW DO?

The proposed legislation was published on Tuesday. It would require May to propose an extension to the Brexit negotiating period, the details of which would need to be approved by parliament.

It does not set out how long the government should seek to delay Brexit for, and notes that both parliament and the EU could propose a different length of extension.

Any extension requires the unanimous approval of the EU.

WILL THE PLAN WORK?

The plan relies on there being sufficient will among lawmakers in both chambers to pass the legislation before April 10, when May is due to attend a EU summit to discuss the next steps on Brexit.

Leaving without a deal on April 12 is the default legal option if Britain cannot present another viable option to EU leaders at that summit.

The government hopes that if the deal already agreed between May and the EU, which has already been rejected by lawmakers three times, is approved this week, it can secure a short extension without having to take part in next month’s European Parliament elections.

The Commons has previously voted to show it does not want to leave the EU without a deal, which could indicate sufficient desire to pass the legislation.

But several lawmakers have expressed reservations about the unprecedented attempt to pass new laws without the government’s approval. The constitutional concerns could sway some to vote against, or seek to stall the process.

The House of Lords is generally seen as being more pro-EU than the Commons, and it would seem likely that a majority exists to support the plan. However, the lack of controls on speaking time may mean opponents could filibuster it.

Legislative experts have so far expressed doubts about whether a piece of legislation proposed this week could be turned into law before April 10.

WHAT HAPPENS AFTER THAT?

Some in the group of lawmakers also want to hold a third round of indicative votes on Monday, in search of an alternative Brexit plan which has the support of a majority in parliament. The two previous rounds of votes have failed, albeit narrowly, to find such a majority.