A former Green Party candidate, Pip Tindall, is to stand in the Westbourne by-election.
Mrs Tindall opposes spending cuts in public services, worse terms or conditions for council staff and above-inflation rises in council tax.
She works for the NHS and describes herself as a trade unionist and welfare rights campaigner.
In the local elections in May she stood as a Green Party candidate for East Brighton, having signed the Brighton Stop the Cuts Coalition pledge.
The pledge meant opposing all cuts and trying to give a political voice to a campaign to have central funding reinstated for public services in Brighton and Hove.
She said that when the Greens were elected she realised that they intended to administer, rather than fight, the Conservative and Liberal Democrat cuts.
Along with her husband, Paul Tindall, she left and joined the Trade Unionist and Socialist Coalition.
“The Green Party says it’s opposed to cuts but that’s just so much hot air if they won’t fight them when they get the chance.
“I was horrified when I realised that the Greens in Brighton intended to hand down the cost of the banking crisis to those least able to afford it – the public service users of Brighton and Hove.
“The working class is being forced to pay for the bankers’ greed.
“We need an inclusive political voice to say ‘No to all cuts’ which the Greens and ‘too far, too fast’ Labour can’t offer.
“Only TUSC is proposing a serious alternative to slash and burn austerity.”
Mrs Tindall supports the industrial action against public sector pension changes which is due to take place on Wednesday (30 November).
The by-election is on Thursday 22 December.