More than half of Rome’s elected councillors resigned en masse on Friday in an attempt to oust the mayor, Ignazio Marino, after he backtracked on a pledge to resign.

Marino, who is embroiled in an expenses row, announced earlier this month that he would step down. But he withdrew his resignation on Thursday, despite his party calling on him to go.

The resignation of 26 councillors out of a total of 48 automatically unseats the mayor and ushers in a temporary commissioner to run the city while new elections are organised, possibly for next year.

Marino, a former surgeon, is one of the most unpopular politicians in Italy, and faces mounting public anger over litter-strewn and potholed streets, a failing public transport system and revelations of mafia infiltration of the municipal authority.

The 19 councillors from the Democratic party, which Marino represents, threatened to collectively resign if he remained in post. When they followed through on their threat, seven councillors from other parties joined them.

Marino was elected with a reputation for personal honesty, but his administration has been buffeted by a series of damaging stories.