Douglas Carswell said his membership was no longer necessary following last year's referendum vote to leave the EU, saying: "I will leave UKIP amicably, cheerfully and in the knowledge that we won."
The announcement comes just days before Prime Minister Theresa May is due to formally notify the European Union of Britain's intention to leave the bloc, starting a two-year countdown to Brexit.
Carswell's ties had long been strained with the rest of the party, in particular its founder Nigel Farage, who has repeatedly tried and failed to win election to the 650-seat House of Commons.
But his resignation is a blow after months of infighting in the party, which is struggling to find a winning platform beyond its core message of euroscepticism and opposition to mass immigration.
Carswell was first elected to parliament in 2005 as a member of May's Conservative party, but resigned in 2014 to stand again as a member of UKIP in the south-eastern English seat of Clacton.
"Like many of you, I switched to UKIP because I desperately wanted us to leave the EU." he wrote in a blog posting today, entitled "Job Done".
"I will not be switching parties, nor crossing the floor to the Conservatives, so do not need to call a by-election, as I did when switching from the Conservatives to UKIP.
"I will simply be the member of parliament for Clacton, sitting as an independent."
He paid tribute to UKIP's efforts, saying that despite their failure to win more MPs, "in a way we are the most successful political party in Britain ever".
"We have achieved what we were established to do -- and in doing so we have changed the course of our country's history for the better," he said.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
