Laurence Fox's Reclaim party lost its only MP on Wednesday after Andrew Bridgen quit over "a difference in direction". Mr Bridgen said he had to put his constituents "first" with an election looming "in the first half of next year".
The North West Leicestershire MP joined Reclaim in May after being expelled by the Conservatives for promoting anti vaccine conspiracy theories and comparing Covid jabs to the Holocaust.
He will now sit as an independent.
In a statement he said: "This morning, I have made the incredibly difficult decision to resign from the Reclaim Party.
"I would first of all like to thank Laurence and all of the team at Reclaim who have been excellent and supported me wholeheartedly for the last nine months.
"I have come to this decision purely because of a difference in the direction of the Party, I will still wholeheartedly support the policies and values of the Reclaim Party and wish them all of the best in their future endeavours
"However, I need to make a very important decision with a general election pending in the first half of next year.
"I need to put North West Leicestershire first, above any Party allegiance."
Mr Fox said the Reclaim party remain "hugely supportive" of Mr Bridgen's campaigning on "a number of issues".
The former Health Secretary called the comments “disgusting and dangerous anti-Semitic, anti-vax, anti-scientific conspiracy theories”.
