Cllr Poole referred himself to the Public Services Ombudsman for Wales and has also been referred to the council’s own standards committee for further investigation.
The new interim leader said: “I want to send a clear message that our focus remains on delivering key services to our residents and supporting the needs of our community and we will not be distracted from this.
“I fully appreciate that the resignation of the leader has caused concern, but this matter needs to be dealt with by the appropriate investigating bodies and we must allow this process to be followed.
“We have developed an ethos of ‘Team Caerphilly’ here within the council and now it is more important than ever that we all work together to deliver on our commitment to provide quality services to all sections of our communities.”
The council has said the process to select and appoint a new leader will take place over the coming weeks.
While the local authority has not revealed details, Caerphilly Observer understands Cllr Poole’s resignation relates to an allegation that he did not declare an interest at a Cardiff Capital Region City Deal meeting.
A spokeswoman for the Wales Audit Office said: “As part of our routine audit work, we issued a letter to the interim chief executive of Caerphilly council. During our annual audit of accounts (for the Cardiff Capital Region City Deal, not Caerphilly council) we identified some issues which we have reported to the council.
“We have no way of knowing whether the leader’s resignation was anything to do with our letter, nor would we want to speculate over this.”