Farage said Yusuf was “a huge factor” in the party’s success in last month’s elections, when Reform won a by-election, two mayoral races and gained 677 new councillors.
“Politics can be a highly pressured and difficult game and Zia has clearly had enough. He is a loss to us and public life,” he wrote on social media.
Deputy leader Richard Tice thanked Yusuf for his “major help in securing such progress and success over the last 11 months”.
“We would not be where we are today without him,” he added.
In a post on X, Yusuf wrote: “11 months ago I became chairman of Reform. I’ve worked full time as a volunteer to take the party from 14 to 30% [in national polls], quadrupled its membership and delivered historic electoral results.
“I no longer believe working to get a Reform government elected is a good use of my time, and hereby resign the office.”
Earlier, Yusuf had criticised Reform MP Sarah Pochin – who won last month’s Runcorn and Helsby by-election – for urging Sir Keir Starmer to ban the burka “in the interests of public safety” during her Prime Minister’s Questions debut on Wednesday.
He said it was “dumb for a party to ask the PM if they would do something the party itself wouldn’t do”.
Pochin’s call appeared to go down well with Reform’s other MPs, although a party spokesman said it was “not party policy”.
Yusuf became Reform UK’s chairman shortly after last year’s general election, after previously being a member of the Conservative Party.
A former banker who sold his tech start-up company for more than £200m, Yusuf has described himself as a “proud British Muslim patriot”.
He revealed that he had donated £200,000 to the party during the election campaign.
As chairman, he was given the job of professionalising the party, wooing donors and increasing Reform UK’s activist base.
Yusuf was seen as central to Reform’s operation and had been leading the party’s so-called DOGE teams to cut wasteful spending in the councils it now controls.
The acronyn refers to Elon Musk’s Department of Government Efficiency in the US.
Liberal Democrat Deputy Leader Daisy Cooper said: “By sacking himself, Zia Yusuf seems to be leading the “UK DOGE” by example. You have to admire his commitment to the cause.
“It’s already clear Reform UK cannot deliver for the communities they are elected to stand up for. Instead, they have copied the Conservative playbook of fighting like rats in a sack.”
