Paul Brothwood is backing Tory MP Mike Wood in Dudley South, saying he fears votes for Nigel Farage’s party could help elect a Labour-Lib Dem government that would stop Brexit.
It came as Mr Farage prepares to unveil hundreds of candidates across the country for the December 12 vote.
Former Dudley Ukip councillor Mr Brothwood had been selected as the Brexit Party’s candidate for the seat in August.
He said: “This has been a huge decision for me personally. I have talked at length with Mike about his vision for our area and I know it’s safe in his hands plus he is committed to delivering Brexit.”
He added that letting Labour in would cause “havoc” to public services, the economy and to community cohesion.
“As a type1 diabetic I know the NHS is safe in Conservative hands,” Mr Brothwood said.
“It feels good to be back in the Conservative family who are committed to delivering Brexit and I am confident that Boris Johnson is the best person to stand up for Britain.”
Welcoming Mr Brothwood to the Conservative Party, Mr Wood, who currently holds a majority of 7,730, said: “I’m really pleased that Paul has decided to back our campaign.
“Having worked with him on the Vote Leave campaign, and served alongside him as a Dudley councillor, I know how much Paul cares about our local economy, our public services and improving the opportunities available for people in our community.
“He shares my vision for our area and our country, and I am delighted that he will now be supporting our work to deliver on it.”
Education Secretary and South Staffordshire MP Gavin Williamson said Mr Brothwood would play a major role in the party.
“Paul has spent many years campaigning to get Britain out of the EU and has recognised the only way to deliver that is by voting Conservative at this election so we can get Brexit done,” he added.
Mr Farage, who is not running for parliament himself, says he is standing candidates in hundreds of seats after Boris Johnson rejected his call for a ‘clean break’ Brexit alliance.
Steve Baker, chair of the Tory European Research Group, warned that the Brexit Party risked stopping the UK’s departure from the EU altogether by “dogmatically pursuing purity”.