Former Conservative MP Heidi Allen, who has joined the Liberal Democrats, said her constituents are happy that she has put the national interest first.
The South Cambridgeshire MP, who has been sitting as an independent since quitting the Change UK group in June, takes the Lib Dem tally in the Commons to 19.
She said her constituents have been “unbelievably supportive” of her decision, and said she believes others will leave the Conservative Party and join the Lib Dems.
Ms Allen told BBC Radio 4’s Today programme she has received thousands of emails and has been stopped in the street, adding: “And almost exclusively people tell me that they’re happy I’ve put the national interests first.
“So of course, when that general election comes, which I think is going to be very soon, they will have the chance to test that.
“And if I’m wrong, then absolutely they will vote for Conservatives as they always have done in South Caambridgeshire, which is typically a safe seat.
“But that’s not the reaction I’m getting from my constituents.”
Her move follows the recent arrivals of ex-Tories Sarah Wollaston, Sam Gyimah and Phillip Lee as well as former Labour MPs Chuka Umunna, Angela Smith and Luciana Berger.
Ms Allen, a committed Remainer, said she was joining the Lib Dems as the other main parties had turned their backs on the “liberal progressive centre ground”.
Speaking about the Conservative Party, Ms Allen told the programme: “The party has changed irreversibly.”
It's become Brexit Party version twoHeidi Allen on the Conservatives
She added: “The party is absolutely not what it was nor has it kept the promises that it made. It’s changed.
“It’s become Brexit Party version two. And that is certainly not what my constituents voted for.”
Asked if she thinks others will leave the Conservative Party and join the Lib Dems, Ms Allen said: “Yes, I do. I think they’re going through a lot of soul searching at the moment, wondering what the best thing to do is when that general election comes, which I think we all know will be sooner rather than later.”
Pressed for a number, she said: “I mean, there’s a good number that have said they’re going to stand down full stop, but I would imagine it must be going through the minds of at least half a dozen others.”
Ms Allen originally quit the Tory Party in February, along with Ms Wollaston and Anna Soubry, to join the new Independent Group, later renamed Change UK, formed by ex-Labour MPs.
The following month it was announced that she had been appointed interim leader but she left three months later amid reports of disagreements over strategy.
Her South Cambridgeshire constituency is traditionally a safe Conservative seat which she held with a majority of almost 16,000 at the 2017 general election.