Former Tory MP and prominent columnist Matthew Parris has said he will quit the party after 50 years in a call for Conservatives who oppose Brexit to support the Liberal Democrats in the election.

The Times journalist said he will cast his vote for the remain-backing party in the 12 December ballot “to defeat Tory zealotry over Europe” as he joined a growing list of prominent members to quit.

His defection followed that of Antoinette Sandbach, who was one of the 21 Tories expelled by Boris Johnson after rebelling over legislation to prevent a no-deal Brexit.

On Friday, Parris wrote: “Despair is no longer enough: finally one must act. So with this column I’m leaving the Conservative party.”

He cited a string of former Tories, some of those expelled and some of those who left under pressure, adding that he could be counted out too.

“I am a conservative not a Liberal Democrat but will unhesitatingly vote Lib Dem to defeat Tory zealotry over Europe, this time,” he wrote. “So should every former Tory voter who still believes it would be folly for Britain to leave the European Union.”

He said there was a lot he would miss about the party added: “But the Tory party has crossed their Rubicon. Now I must cross mine.”

On Thursday, Sandbach criticised the Conservatives for offering “years of uncertainty” over Brexit as she joined the Lib Dems to contest her Cheshire seat of Eddisbury.

Like former chancellors Philip Hammond and Ken Clarke, she did not get the whip back before the successful vote to hold a general election. Ten MPs did get the whip returned.

Lib Dem leader Jo Swinson will join her latest recruit from the Tories, Sam Gyimah, on Saturday as he launches his campaign to take London’s Kensington seat from Labour.

Gyimah is a former minister who gave up his membership while criticising the Tories for becoming a “hard Brexit party”.