Alliance Party leader David Ford has complained to the PNSI over the lack of charges over alleged dirty tricks against his party at last year's election.
Mr Ford has written to Chief Constable Sir Hugh Orde and the Electoral Commission after the PSNI told him there was little chance they could secure a conviction.
The allegation centred on campaign leaflets in Alliance colours that were sent to Alliance supporters urging them to vote tactically for the Ulster Unionist party (UUP). The leaflets were signed by a group calling itself Concerned Citizens for a Shared Future.
The Alliance Party was convinced the campaign was orchestrated by the UUP. Outraged at thousands of leaflets being distributed, the party complained to the PSNI in east Belfast in April last year who turned the issue over to the electoral commission.
The PSNI said today the issue had been referred back to them in June this year and that their legal advice was that a successful prosecution would be unlikely.
Mr Ford said he had been dismayed when the decision was relayed to him. He said one of the reasons given for not pursuing the matter was a lack of co-operation by those being investigated.
"This sounds to me an extraordinary reason to drop a criminal prosecution," he said. "If you compare what used to happen in elections some years ago, you'd frequently hear of one or two people arrested for personation . . . and they would be prosecuted for attempting to steal a vote.
"Here we have a case where it appears tens of thousands of bogus leaflets in defiance of the election spending limits are issued yet the police aren't intending to do anything," Mr Ford said.