A Liberal Democrat councillor has defected to Labour in support of Jeremy Corbyn, becoming Richmond's first Labour councillor in more than 13 years.
Teddington Councillor Jennifer Churchill, partner of the borough's former Lib Dem leader and fellow Councillor Stephen Knight, said new party leader Tim Farron "doesn't seem to stand for anything".
She also criticised her former party for "parroting Tory economic propaganda".
Coun Churchill told the Richmond and Twickenham Times, in her first interview since defecting: "I wouldn’t say [it has been coming] for a long time – when Jeremy Corbyn was elected, it became a real possibility.
Coun Churchill's Lib Dem councillor partner Councillor Stephen Knight supports her decision
“The Labour Party’s policies are more in line with my own views.”
She said that her Lib Dem councillor partner Coun Knight was “quite supportive” of her decision to defect.
Coun Churchill added: “Generally speaking, we are quite supportive of each of each other.
“So far the only people who have reached out to me have been very kind and supportive and have congratulated me on my bravery, but I imagine there will be some disgruntled people too.
“I will do my best to be a robust opposition.
“I think on the whole things will be very similar to how they were before.
“There is now a Labour presence in the borough and I think it is great they will have someone to speak on their behalf on the council.”
She added: "Despite the coalition having ended, and a new leader having been installed, last weekend has shown that the Liberal Democrats are happy to continue parroting Tory economic propaganda in place of acting with either political courage or intellectual rigour.
"Tim Farron doesn’t seem to stand for anything – making him in this sense even worse than Nick Clegg."
She said she will continue to fight for a better deal from the Conservative council on issues including childcare and housing costs.
Coun Roberts said Coun Churchill left the Lib Dems on "extremely good terms"
Richmond Lib Dem leader Councillor Gareth Roberts said she had left the party on "extremely good terms" and said he would continue to work closely with her on a cross-party basis.
He added: "Though she may no longer be a member of the Lib Dems, I'm sure Jennifer will continue to be supportive of our work as the only local party capable of providing a credible alternative to Nick True's increasingly arrogant and out of touch Conservatives."
Coun Churchill’s partner, Liberal Democrat London Assembly member and former leader of Richmond’s opposition, Stephen Knight, said the couple, who have two children, have very similar political views but he remains loyal to his party.
He said: “She decided after quite a lot of thought that the best place for her is in the Labour Party and I support that decision.
“My view is that I can further my causes that I believe in strongly more effectively from where I am as a member of the Liberal Democrats.
He added: “I have been fairly outspoken about the Lib Dems and the coalition, which I did not support, and their current position vis a vis austerity economics.
“I think we have quite similar views on these issues but I have chosen to stay and fight my corner for the Lib Dems.”
Stephen Knight said he would not have thought Coun Churchill’s defection would lead to calls for a byelection from Richmond’s Liberal Democrats.
He refused to be drawn over whether she would have defected from the Lib Dems were he still leader.
Coun Knight said: “That is impossible to say; I am not still leader though I don’t know what difference that would have made, if any.
“I am supportive of her decision, which is the right one for her, and I respect that decision.”
When Coun Knight was asked whether he tried to persuade his partner to remain in the party he answered: “That is not how our relationship works.”
Leader of the council Lord True paid tribute to Coun Churchill, describing her as "delightful person" and "one of the most genuine councillors on the council".
Council leader Lord True said Coun Churchill will be an asset to the Labour Party
He added: "I’m sure she will be an asset to the Labour Party, however, it is a strong vote of no confidence in the Lib Dem leadership of Gareth Roberts.”
He added the council will have to look at the make-up of its various committees and work out how it will move forward.
Deputy leader of the council, Councillor Geoffrey Samuel, speculated more could follow Coun Churchill in leaving the Lib Dems.
He said: “It is an enormous slap in the face for them to announce it during their conference when their new leader said they were expecting Labour people to defect to them.
“This is obviously a real blow to the new leadership of Roberts and Ehmann and the way that those two perform.
“She won’t be the last to leave them and the real question is who is next?”
Coun Samuels defected from Labour to the Tories in the 1960s, but was not a sitting councillor at the time.
Nick Grant, who stood as a Labour candidate in Twickenham in May's General Election, said the defection is an example of his party growing in the borough.
Labour's Nick Grant said his party will provide a "strong alternative" to the Tories
He said: "As the Labour movement continues to grow with local councillors like Jennifer joining the ranks, we’ll continue to focus on the things that matter, providing a strong alternative to the Tories and always putting residents first."
Former Twickenham MP Sir Vince Cable suggested last week that the Lib Dems could disband and create a new liberal party, along with Labour moderates and disaffected Tories.
Baroness Jenny Tonge, former Lib Dem MP for Richmond Park, told the Sunday Times this week that she was considering lending her support to new Labour leader Jeremy Corbyn.
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