By Andrew MacAskill and Alistair Smout
LONDON (Reuters) - Tens of thousands of people opposed to Britain's withdrawal from the European Union gathered to march through central London on Saturday to demand a new referendum as the deepening Brexit crisis risked sinking Prime Minister Theresa May's premiership.
After three years of tortuous debate, it is still uncertain how, when or even if Brexit will happen as May tries to plot a way out of the gravest political crisis in at least a generation.
May hinted on Friday that she might not bring her twice-defeated EU divorce deal back to parliament next week, leaving her Brexit strategy in meltdown. The Times and The Daily Telegraph reported that pressure was growing on May to resign.
"It's intolerable, the situation that we're in, and I'm afraid Theresa's the problem," Anna Soubry, a pro-EU lawmaker who left the Conservative party to join the Independent Group in February, told BBC TV.
"She has to go, and we need some temporary prime minister who can reach out, put the country first, and get this back to the British people. That's what we're all marching for today."
While the country and its politicians are divided over Brexit, most agree it is the most important strategic decision the United Kingdom has faced since World War Two.
Pro-EU protesters gathered for a "Put it to the people march" at Marble Arch on the edge of Hyde Park around midday, before marching past the prime minister's office in Downing Street and finish outside parliament.
While there was no official estimate of the numbers, a Reuters reporter said tens of thousands of people had gathered even before the event officially started.
Organizers were confident that the size of the crowd would exceed a similar rally held in October, when supporters said about 700,000 people turned up.
"NEVER GONNA GIVE EU UP"
Phoebe Poole, 18, who was holding a placard saying "never gonna give EU up" in reference to a song by 1980s popstar Rick Astley, wasn’t old enough to vote in the 2016 referendum.
"We have come here today because we feel like our future has been stolen from us. It is our generation that is going to have to live with the consequences of this disaster," she told Reuters.
"It is going to make it harder to get a job. You are already seeing a lot of large companies leaving. I am worried about the future."
Two hundred coaches from around Britain were booked to take people to London for the march. One coach left the Scottish Highlands on Friday evening, and another left from Cornwall on England's western tip early on Saturday morning.
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.
May has repeatedly ruled out holding another Brexit referendum, saying it would deepen divisions and undermine support for democracy. Brexit supporters say a second referendum would trigger a major constitutional crisis.
Supporters of Brexit say that while the divorce might bring some short-term instability, in the longer term Britain would thrive if cut free from what they cast as a doomed experiment in German-dominated unity that is falling far behind other major powers.
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."