A complaint has been made to police against Shropshire Council's leader.
Earlier, Keith Barrow said he was quitting as leader of the Conservative-run authority and as a councillor.
He recently accepted failing to comply with the council's code of conduct by not declaring a relationship.
West Mercia Police said it had received a complaint regarding "misconduct in public office involving a man from Shropshire". Mr Barrow said he was unaware of the complaint.
The BBC understands the complaint relates to the Conservative leader.
The police force said: "We can confirm we have received a complaint regarding misconduct in public office involving a man from Shropshire. We are currently reviewing this."
In a statement earlier, Mr Barrow said he was "proud" to have contributed ideas in the "most challenging of financial times for local authorities" and council tax had been frozen for seven years.
He stood down after failing to declare a relationship with the director of an accountancy firm appointed to work with the authority's private company, IP&E.
He apologised and also resigned as director of IP&E, following the findings of an internal investigation.
Mr Barrow said his intention to retire meant the people of Shropshire were not getting all they could from him. A new leader is to be elected at the next meeting of full council on 17 December.
"Presently, the council is working on its financial strategy up until 2020 and the leader of the council should be involved in leading that project," Mr Barrow said.
The council's chief executive Clive Wright said these were "unprecedented times of change and budget cuts for local government" and the "enormous pressure upon councillors, particularly the leader and cabinet, should not be underestimated".
Joanne Gallacher, BBC Shropshire Political Reporter
In recent weeks, Oswestry councillor Keith Barrow has come under increased pressure and at one stage was forced to apologise after an investigation found him guilty of breaking the council's code of conduct.
He had failed to declare his personal and business relationship with a director of the firm that was appointed accountants and auditors of the council's private company IP&E.
This is not the first time he has been investigated - in 2010 there was a complaint about his conduct. It was alleged he failed to declare he was the director of a company but the authority decided not to take the allegation any further.
There has been disquiet among colleagues in the Conservative group for some time. Mr Barrow was elected in 2009 and became leader shortly after.
He has had to deal with crippling cuts and has been admired for taking up the role during a difficult time.