The former chairman of a Medway Labour group set up to support Jeremy Corbyn has left the group, saying she is “disgusted” by his “cheap moves”.

Rachel Garrick has stood down from Medway Momentum after the Labour leader opposed the construction of a new nuclear power plant at Hinkley Point in Somerset, which would have created 27,000 jobs.

Mrs Garrick, who lives in Rochester, is a member of the Prospect Trade Union, which represents engineers, scientists, managers, and has been negotiating to secure jobs at the site.

In a Tweet she said: “I’m disgusted by Corbyn’s cheap moves on Hinkley. He’s betrayed the tireless work of Unite, GMB and UCAT. I will no longer be voting for him.”

This was followed by a tweet announcing her resignation from Medway Momentum. She has now switched allegiances and is supporting Owen Smith’s campaign to become the next Labour leader.

Mrs Garrick resigned as chairman of the group around two months ago, as she is moving to Wales.

Medway Labour councillor Tris Osborne, who also supports Mr Smith, said Medway Momentum needed to “take a look at itself”.

He added: “It’s pretty clear now that Corbyn is not connecting with people in Medway. They’re haemorrhaging members now and we’re gaining quite a lot of people to support Owen Smith that previously supported Jeremy Corbyn.”

In a Facebook post, Mrs Garrick, who co-founded Medway Momentum, said she had received criticism for dropping her support of Mr Corbyn over a single issue.

She wrote: “Whilst Hinkley may be a single issue to many, please do bear in mind and respect that I am the only branch councillor who represents the EDF Hinkley Point Project for Prospect Trade Union.

“I have the job of representing several hundred members in the biggest union on the project. No other trade union represents nearly as many workers as we do in this area.

“I have worked for five years on this project. I have sat with French Trade Unions trying to negotiate a stable resolution for the project. I have negotiated with directors. I have helped colleagues through redundancy. I have shouted for support at the 6ft 5in vice president of our trade union. I have seen more stress than I care to admit.”

Mrs Garrick told The Huffington Post that Mr Corbyn was out of touch with rank and file trade unionists and she had friends in the movement who were also “wavering” because Corbyn was proving that he “isn’t the genuine left wing socialist he claims”.