Nigel Farage warned the Gorton and Denton by-election was a "victory for sectarian voting and cheating". Labour was pushed into third place in the former stronghold behind Zack Polanski's party and Reform UK.
In a post on X, Reform leader Mr Farage sad: "This election was a victory for sectarian voting and cheating. Matt Goodwin was a great candidate for us. Roll on the elections on May 7th. It will be goodbye Starmer and goodbye to the Tory party."
The Greens faced accusations of sectarian politics by sharing campaign material in languages including Urdu and Bengali calling on voters to "punish" Labour over Gaza.
One video showed Sir Keir Starmer shaking hands with Indian PM Narendra Modi, who is unpopular in Pakistan, and David Lammy with Israeli leader Binyamin Netanyahu.
Reform candidate Matt Goodwin said: "We are losing our country. A dangerous Muslim sectarianism has emerged.
"We have only one general election left to save Britain. Vote Reform every chance you get.
"I will continue the fight. I will always fight for you. I will stand at the next general election. Matt."
*** Ensure our latest politics headlines always appear at the top of your Google Search by making us a Preferred Source. Click here to activate or add us as Preferred Source in your Google search settings. ***
New Green MP Hannah Spencer denied accusations of sectarianism in an interview after her win.
She told the BBC: "I think all of us know what it feels like to be shut out of a system that isn't built for us and I will always go out of my way to try and include people who may be struggling to access something.
"And I'm really proud that we were just different and we showed people that we were going to try and reach them if they'd been let down by other politicians."
Pressed why the image of Sir Keir with Mr Modi was used, she added: "I've just been out every day talking to people, listening to people and when people weren't able to access information in a way that other people might, we tried to give literature and information in a language they speak and I'm really proud we did that."
