Nigel Farage's Brexit Party has called for an investigation into allegations of impropriety during Labour's slim victory in the Peterborough by-election.
The leader urged an end to the postal votes system in its current form, as party chairman Richard Tice said there had been numerous "rumours" including of "vote-rigging".
Cambridgeshire Police, however, have said no offences have been revealed in respect to one allegation of bribery and two relating to postal votes during its ongoing investigation.
Labour's Lisa Forbes won the June 6 poll by 683 votes, narrowly pushing out the Brexit Party into second place.
Mr Tice called for "answers" and said his party would lodge a petition under the Representation of the People Act 1983 later this week.
Cambridgeshire Police continue to investigate two allegations - one of a breach of the privacy of the vote and one of the burning of ballots.
But the force has announced that no offences were found over allegations of bribery relating to postal votes.