Coun Martin Mitchell, who represents Layton, said he made his decision after being given the cold shoulder by Labour colleagues who stripped him of his role as chairman of the tourism, economy and communities scrutiny committee last year.
He will continue to represent his constituency as a non-aligned independent councillor.
Labour had already lost overall control following the departure from the party of former leader Coun Simon Blackburn last July, although he said he would continue to support his former party in the council chamber.
Coun Mitchell's decision leaves the council with 20 Labour councillors, 16 Conservative, two Blackpool Independents and four non-aligned independents.
In July 2020, Coun Mitchell had defied his party colleagues when he used his casting vote to refer an executive decision over proposals to redevelop the Stanley Park Golf Course back to full council.
A reshuffle in May 2021 saw him replaced by Coun Fred Jackson in the £10,500 a year chairman's role.
Coun Mitchell said: "Last year the leadership of the Labour group deliberately antagonised me by removing me from the position of chairman ofthe tourism, economy and communities scrutiny committee without consultation, indeed I was given no explanation beforehand or afterwards.
"Their only contact with me since has been to threaten disciplinary action after I went public with my reaction."
He said support he had sought from the regional Labour Party had also been unforthcoming, and he had become disenchanted by the party at a national level, including treatment of its left wing members.
He added: "If the party is not going to behave with rudimentary fairness then it doesn’t deserve my support or my loyalty.
"I am sensitive to the argument that since I was elected as a Labour councillor I should now leave Labour. It would be more accurate, however, to say Labour has left me.
"As of today I am an independent councillor. I remain intensely proud to represent the people of Layton and will continue to do my utmost for them."
Blackpool Council and Labour group leader Coun Lynn Williams said: "We are sorry to lose members of course but it is very much business as usual,.
"We will continue with our progressive policies and the regeneration of the town, to continue to build on the successes to date."
Coun Mitchell is the third councillor to leave the Labour group during the current administration.
He has represented Layton since 2011, was previously a Labour councillor in Berwick-upon-Tweed and stood as Labour candidate for Fylde at the 2019 General Election.
Former leader Coun Simon Blackburn left the party in July 2021 following an investigation into his conduct, while former deputy leader Coun Graham Cain was expelled by Labour in summer 2020.
Coun Blackburn has announced he will step down from his seat, representing Brunswick ward, at the next local elections in Blackpool, which are due to be held in May 2023.