Burnley Borough Council's leader and nine other councillors at the authority have left the Labour Party over Keir Starmer's stance on the conflict in Israel and Gaza.
It takes the number of Labour councillors at Burnley from 22 to 12, out of 45 total seats.
Lancashire county councillor Usman Arif, who represents Burnley North East, has also left the party.
The councillors said in a statement: ‘Since the onset of the violence in Gaza/Israel, we, as a collective, have consistently used our roles as councillors to advocate on behalf of our communities to bring peace by urging the leadership to call for a release of all hostages and an immediate ceasefire.
‘We strongly condemn the loss of any innocent life without reservation.’
They had urged Mr Starmer to call for a ceasefire, and later called on the Labour leader to resign.
The councillors added: ‘We always felt it was our responsibility as elected members to work to effect change from within.
‘However, despite our persistent endeavours, it has become apparent that Keir Starmer and the leadership either cannot or will not heed our concerns or acknowledge the sentiments within our communities.’
They said they were resigning with immediate effect and would continue to represent their communities as independent councillors.
The resignations come after Labour lost its majority on Oxford City Council when nine councillors resigned from the party over its stance on the conflict.
Senior Labour local government figures have joined calls for a ceasefire in Gaza, including London mayor Sadiq Khan and the mayor of Greater Manchester, Andy Burnham.
