Former Conservative minister and leadership contender Sam Gyimah took to the Liberal Democrat conference stage amid wild adulation as he confirmed he had become the sixth MP to defect this year.
Rumours had swirled since Friday that the Lib Dems were gearing up for a big announcement at the party conference in Bournemouth.
Leader Jo Swinson kept members waiting until well into the evening on the first day to reveal that Mr Gyimah – a former aide to David Cameron when he was prime minister – had become a Lib Dem MP.
Mr Gyimah, who represents East Surrey, sat as an Independent after losing the Tory whip when he backed a move by opposition parties to prevent a no-deal Brexit earlier this month.
He has been a prominent advocate of a second referendum and was briefly in the race to replace Theresa May as Conservative leader in June.
The former universities minister told the packed Bournemouth International Centre on Saturday that he had “not taken this decision to be here lightly” but that the Brexit fallout had convinced him to join Mrs Swinson’s party.
He resigned from the frontbench in November over the terms of Theresa May’s Withdrawal Agreement and has been a vocal critic of the deal since, telling Lib Dem members it was “the worst of all worlds”.
Mr Gyimah said he had initially asked Mrs Swinson whether she would stand down the Lib Dem candidate in his constituency to allow him to stand as the sole independent Remainer but she declined.
Referring to her response as “feisty”, he said: “She looked me dead in the eye and said, ‘Sam, I’m in the business of creating Lib Dem MPs and not finding a way back for Conservative MPs’.”
The Ghana-raised politician said he had joined the party to fight for “liberal values”.
“We cannot perceive that our institutions and democracy are immune from populism and nationalism that has tainted other democracies,” he said.
“The Liberal Democrats have a unique opportunity to make sure that we fight to defend these values and create a new force in British politics.”
Wearing orange trousers to match his new party’s colour, Mr Gyimah was heavily critical of Prime Minister Boris Johnson’s approach to securing a Brexit deal.
He said he believed the PM had left himself no option but to pursue a no-deal exit.
“There is now no orderly way for the UK to leave the EU on October 31,” he said.
Mr Gyimah scolded the PM for “playing fast and loose with our constitution” in the way he had hinted he might not obey the Benn Bill – the law passed last week that demands a Brexit extension until 2020 is sought if no withdrawal agreement is in place by October 19.
“Essentially, a government that has made law enforcement the centre-piece of its programme, more police officers to make sure its citizens obey the law, is saying to us it will pick and choose which laws it respects – that is incredibly dangerous,” he said.
“When you are playing fast and loose with our constitution, when you are playing fast and loose with people’s livelihoods, when you are playing fast and loose with people’s security, I think it is right that we all stand up.
“But when people stand up, you’re called collaborators. You’re called saboteurs. You’re called mutineers. Something has gone wrong.”
He accused both Mr Johnson and Labour leader Jeremy Corbyn of presiding over “intolerant” political parties.
Mr Gyimah follows both Dr Philip Lee and Dr Sarah Wollaston in having switched from Tory allegiance to the Lib Dems. Ex-Labour MPs Luciana Berger, Chuka Umunna and Angela Smith have also joined since January.