Six Labour councillors, including a prospective deputy mayor, have resigned from their posts in Lancashire.
The councillors were re-elected in last week's elections
The members of Blackburn with Darwen Council, re-elected in last week's elections, blamed concerns about the workings of the local Labour Party.
The councillors now plan to set up an independent group and say they will resign from Labour altogether.
Labour leader Kate Hollern said the councillors have betrayed those who voted for them less than a week ago.
The councillors who resigned include Mahfooz Hussain, a member of the Labour cabinet and Yusuf Jan-Virmani who would have become deputy mayor.
"It was a very hard decision for me and my family [because] of the people who voted me in as a Labour councillor," Councillor Jan-Virmani told BBC Radio Lancashire.
He claimed that certain elements in the party had not supported him properly in his work.
"I've been in the job for 10 years now and there has been a personal vendetta against me," he said.
"So it's time that I made a stand to go independent."
Mr Hussain stressed the group would be working for the interests of the public.
Robbed and cheated
"We want to promise the voters out there, the community out there, we want to work together and make sure we provide quality services," he said.
But Ms Hollern said she was saddened by the decision.
"The thousands of people in those wards that are affected have been let down so badly," she said.
"They must feel robbed and cheated. They voted for a party not for an individual - and these people have used that to get a position and then gone independent."