Caerphilly County Borough Council leader Dave Poole has resigned after an investigation was launched.
While the local authority has not revealed details, Caerphilly Observer understands it relates to an allegation that Cllr Poole did not declare an interest at Cardiff Capital Region City Deal meeting.
A council spokeswoman said: “A matter has been brought to our attention involving the leader of council that requires further investigation.
“The leader has referred himself to the Public Services Ombudsman for Wales and he will also be referred to the council’s own standards committee for further investigation.
“In light of these actions, the leader has today (Friday, September 20) announced he is standing down to allow appropriate enquiries to take place.
“We are unable to add anything further at this stage.”
Cllr Poole, who became council leader in 2017, will continue as a councillor for the Pengam ward.
Caerphilly Observer understands that Cllr Poole’s decision to stand down as leader is unrelated to the ongoing senior officer pay scandal or the row involving the closure of Pontllanfraith Leisure Centre.
Cllr Barbara Jones, deputy leader of the council, has taken over as interim leader.
Christina Harrhy, interim chief executive of the council, sent a message to all council staff informing them of the news.
The council’s Labour group is set to meet on Monday, September 23 to discuss the issue.
Councillor Colin Mann, leader of the Plaid Cymru group on Caerphilly County Borough Council, said: “Today’s news of the council leader stepping down has come completely out of the blue. As councillors, we’ve not been aware of the reasons.
“This latest episode only serves to erode even further the confidence of the people of Caerphilly county in the Labour leadership of the authority.
“It has presided over the senior officers’ pay scandal, which still has not concluded and has cost millions of pounds of public money, along with the flawed decision making over the proposed closure of Pontllanfraith Leisure Centre and the shutting of public toilets.
“This is an authority in crisis and residents are entitled to question ‘what will happen next’? Can anyone still have confidence in this authority.”