Hundreds of supporters of the campaign were at the rally in Camden, north London, to hear speeches from Sir Patrick, Ms Soubry, Mr Umunna, Lib Dem MP Layla Moran and Caroline Lucas, a co-leader of the Green Party.
Opponents of Brexit staged a "people power" rally in London yesterday to push for a vote on the final exit deal.
More than a thousand people packed into the Electric Ballroom for the raucous launch, complete with t-shirts, flags, posters and pints on Sunday afternoon. And why? Because unity, common cause, wellbeing of society and debate were paramount to belief of this fictional character.
Lawmakers from the governing Conservative Party, as well as the opposition Labour, Liberal Democrat and Green parties, and Sir Patrick addressed the crowd.
"That we shouldn't worry about the cost and complexity of it or the litany of broken promises".
'It is not Charles Xavier standing here in front of you - although I can assure you that if he was, he would have voted Remain, ' he said.
The actor says his two iconic characters would be anti-Brexit, but Boris Johnson says we can live long and prosper outside the EU.
Sir Patrick told the crowd that the day Britain joined the European Union on January 1, 1973, was one of the best days of his life.
'Our country's future is at stake and we will not stand idly by.
Conservative MP Anna Soubry said: "Us MPs made a decision that we would have a referendum".
It draws together nine grassroots campaign groups in a joint effort for a vote. "That is why I support a people's vote on the final deal". One of the them is Open Britain.
"These people just want to keep re-running the referendum until they get the answer they want".
James McGrory, the executive director of Open Britain, said: "When we have been going around to local communities and talking to people about Brexit, there's a real feeling that people are being shut out of a debate in London and Westminster".
"They are elitists who think they know best and don't want to respect the will of the British people".
James added that, if the campaign is successful, the question on the referendum ballot paper will be "between leaving with the deal on offer or remaining with the The People's Vote campaign will demand voters are given the final say rather than Parliament on the deal secured by Prime Minister Theresa May".