Mark Ralph said he has quit the party because of its treatment of ousted Tory councillor Jamie Chowdhary by Reading East Conservative Association (RECA) and the attempts to terminate his own membership because he spoke out in support of his Peppard ward colleague.
He said the attempts were only thwarted when a panel was set up by Conservative Party HQ last year to investigate the controversial de-selection of Mr Chowdhary, who resigned last month and has begun legal action against senior RECA members.
It is understood the panel ruled against his membership termination but supported the de-selection and its process.
Cllr Ralph, who will stay on the council as an independent, also backed Mr Chowdhary's claims that he was targeted after his de-selection with allegations of homophobia in a bid to justify the move, discredit him publicly and to derail his attempts to be selected a candidate by the Reading West branch.
He said: "No political group is free of rivalries and leadership bids but, it is my view that the primary objective of politicians, should be service to the community they have been elected to represent.
"The building of personal power‐bases and squabbling within groups is destructive, time‐consuming and detracts from this. It is our residents that suffer."
Cllr Ralph added: "It's not just the rank injustice to Jamie, a hardworking and respected councillor, it is also the blatant attempt to then undermine his application to be a candidate in Reading West and a sustained campaign, since the panel's report, to make false allegations, jeopardising his public reputation and position as a respected member of the Thames Valley Police Authority.
"To undertake such a vicious campaign when Jamie was unwell was contemptible and Reading East Conservative Association is not an organisation to which I wish to belong."
Cllr Ralph, who was first elected to Reading Borough Council eight years ago, had already jumped ship and joined Reading West, along with Mr Chowdhary and former Tory council leader, Andrew Cumpsty.
He said it was with "sincere regret" that he leaves the Reading West branch, which he said "protected" his status as a councillor while "those in Reading East were seeking to remove him" and gave him time to consider his future.
Cllr Ralph added: "I have great respect for Alok Sharma MP and the administration of RWCA. The association is not run as his personal fiefdom and the management comprises a good cross section of members.
"If I lived in Reading West, Mr Sharma would get my vote every time. I remain a strong supporter of Conservatism. "
He also claimed the reason for his resignation as the Tory group's education spokesman last month was because he had been asked to distance himself from his ousted colleague and a row over the contents of a website, PeppardWard.com which is run by Mr Chowdhary.
When asked why Cllr Ralph resigned, group leader Tim Harris told The Chronicle last month it was "private".
Cllr Ralph said he is cutting all ties with the Conservative Party and added: "I do so with some sadness, but I look forward to devoting more time to my residents.
"I fully expect some vindictive sniping and smear tactics, but I ask now that people dismiss it for what it is, while I get on with the job of serving the people of Peppard ward for as long as they care to elect me.
"As well as addressing my residents' day to day issues, I shall continue to pursue my particular interests in education, children's services, services for the elderly, community care and neighbourhood policing."
RECA chairwoman, Alison Swaddle, said: "Whilst it is always disappointing that anyone decides to leave the Conservative Party, Reading East Conservative Association is not surprised that Mark Ralph has chosen today to leave the party to sit alone in the council chamber as an independent councillor.
"It has been clear for some time that Cllr Ralph felt unable to operate as part of the team.
"The panel report upheld the conduct of RECA and its officers and asked that Cllr Ralph's membership not be terminated only in a bid to avoid inflaming the situation.
"Sadly Cllr Ralph has not heeded the report's call to move forward and unite. Mark Ralph has chosen to leave the Conservative Party but to remain a Peppard ward councillor.
"He was elected by local people as a Conservative councillor with the support of the local party and should now resign his seat and let the people of Peppard ward decide whether they want to be represented by a Conservative or an Independent at a by-election."