LONDON — Hundreds of thousands of pro-Europeans from across Britain marched through London on Saturday calling for another referendum on EU membership with the country mired in political paralysis over Brexit.

Opponents of Britain’s departure from the European Union gathered near Hyde Park before converging on Westminster in what organizers are calling the “Put it to the people march”.

Speakers including Scotland’s First Minister Nicola Sturgeon, London Mayor Sadiq Khan and opposition Labor deputy leader Tom Watson addressed the crowds at a mass rally outside parliament.

“Brexit is a complete and utter mess,” Khan said on the eve of the event.

The protest — one of the largest in the capital in decades — comes after EU leaders this week granted a delay to Brexit, prompting Prime Minister Theresa May to make a renewed bid to win MPs’ backing for her divorce deal.

However she faces daunting odds with lawmakers deadlocked for months over how to implement the 2016 referendum vote to leave, reflecting bitter divisions nationwide.

If she succeeds, Britain — which was staring at a cliff-edge deadline of March 29 for leaving the EU — will depart on May 22 under the terms of the withdrawal agreement the prime minister struck with Brussels last year.

But if lawmakers defeat the accord again, as expected, London must outline a new plan or face a no-deal Brexit as early as April 12 — unless it decides to request another extension and hold European Parliament elections in May.

Any further delay would likely prompt further calls for another referendum as the only way out of the impasse.

A petition to cancel Brexit altogether gained 4 million signatures in just 3 days after May told the public “I am on your side” over Brexit and urged lawmakers to get behind her deal.

In the June 23, 2016 referendum, 17.4 million voters, or 52 percent, backed Brexit while 16.1 million, or 48 percent, backed staying in the bloc.

But ever since, opponents of Brexit have been exploring ways to hold another referendum.

Some opinion polls have shown a slight shift in favor of remaining in the European Union, but there has yet to be a decisive change in attitudes.

Many voters in Britain say they have become increasingly bored by Brexit and May said on Wednesday that they want this stage of the Brexit process to be “over and done with.” — Agencies