Ian Austin said he "warned" his party what would happen if Jeremy Corbyn led Labour into an election.
The former Labour MP for Dudley North – who turned Independent before his resignation earlier this year – said he was "proud" of the people of the Black Country for "rejecting extremism and racism" in voting for the Tories over Labour.
Mr Austin said: "People like Jeremy Corbyn, John McDonnell, Len McCluskey and the rest of the hard-left gang that led Labour to its record defeat must be shown the door before the party can even begin to think about rebuilding.
"And Momentum – the party within a party set up to defend Corbyn – must be booted out too.
"People would never have believed results like we saw on Thursday could have been possible, but it was clear from Thursday night’s exit poll that Britain was heading for an earthquake.
"And the decent patriotic voters in my old seat in Dudley turned the town blue by sending a Tory MP to Westminster with more than 12,000 votes over Labour.
"They can’t say they weren’t warned. Even before he was elected leader I told the party that Britain would never put an extremist in Number 10.
"I knew people in places like Dudley could never imagine these people running the country or standing up for us abroad.
"Decent patriotic people want leaders they can trust to defend us. They believe that hard work pays off and want our borders protected. They won’t stand for racism.
"Corbyn and the rest of them failed all these tests."
He added: "We spent the election warning that the Labour Party has been poisoned by racism, extremism and intolerance under his leadership.
"We should be proud that our country has stood up for decency and rejected racism, but we must also resolve that Jewish people must never again be made to feel scared in Britain.
"I disagree with lots of things the Government has done but only two people could have been Prime Minister today and I have always said that Jeremy Corbyn is completely unfit to lead our country.
"I worked really hard to persuade the Labour Party to replace him with a decent leader and I warned them what would happen if he led Labour into the election so I wish this had not been the choice, but I am proud of people in the Black Country who rejected extremism and racism."
Mr Austin said his old party had a "long and hard road back to respectability and relevance".
"I am going to keep campaigning for mainstream decent values in politics and arguing against populism and extremism," he added.
"And we all have a big job to do to stand up for mainstream democratic values and beat the extremists for good.
"But I’m optimistic about that because I could not be prouder of the British people.
"They have rejected extremism and the poisonous hate which the hard left brought into the Labour Party.
"And they have stood up for Britain’s Jewish community, rejected racism and said enough is enough."