Sinclair told the BBC he felt he was being “stitched up” by being honest and outspoken.
“I was elected unopposed in 2021 and I’ve been a constant thorn in [the council’s] side,” he said.
“What you see is what you get with me – I don’t have anything to hide.
“I actually feel quite good about things, because I don’t have to put up with any of it any more.
“People in Ledbury know I’ve done a lot for the town, I’ve assisted residents with all sorts of things.”
Sinclair, a former Conservative, said he was now a member of Reform UK and intended to help the party in next year’s Herefordshire Council elections.
Councillor Liz Harvey, chair of the town council, said: “On behalf of Ledbury Town Council, I can confirm that Mr Sinclair has tendered his resignation as a town councillor.
“Since joining the council Mr Sinclair has had a number of code of conduct complaints investigated and upheld against him.
“On each occasion, Mr Sinclair has refused to comply with the recommendations of the monitoring officer as regards undertaking relevant training and making appropriate apologies for his actions.
“A further complaint regarding his behaviour is about to be determined.”