Police are still investigating nine separate complaints of potential electoral fraud in the West Midlands.
West Midlands Chief Constable Paul Scott-Lee told a police authority meeting that he could not rule out the possibility of criminal charges resulting from any of the ongoing inquiries.
He said the incidents related both to the recent General Election and last year's Birmingham City Council elections, after which two Aston Labour councillors were found to have committed systematic postal-vote fraud and were barred from public office for five years.
Mr Scott-Lee said: "The majority of issues that were brought to our attention were genuinely raised but when researched were found to be quite bona fide.
"There are something in the order of nine ongoing inquiries that are yet to be finalised dealing with the General Election and the previous local election.
"I can't say there wouldn't be criminal proceedings coming out of these because the work has not been completed yet."
Last June, officers attended a warehouse in Witton where they discovered Labour councillors and supporters surrounded by 275 unsealed postal votes.
The incident, one day before the council elections, formed the central part of an election fraud court hearing in Birmingham earlier this year.
Elections Commissioner Richard Mawrey QC criticised the "Olympian detachment" with which the force had reacted to electoral malpractice during the case.
He said at the time: "The reaction of the police can be best summed up by drawing attention to the code name they gave to complaints of malpractice - Operation Gripe."
However, Mr Scott-Lee said the General Election earlier this month had been the most heavily policed in many years and senior officers had provided advice and guidance to forces across the UK.