The BBC reports:
Bournemouth Borough Council has been notified by the High Court an election petition has been submitted challenging the result in the Kinson South ward.
It has been brought by unsuccessful Labour candidate Beryl Baxter.
Ballot books featuring candidates from neighbouring Kinson North ward were incorrectly sent to polling stations.
The error also occurred the other way round, meaning a number of voters were unable to cast their votes in both wards.
Once the problem was discovered, correct ballot books were delivered to the polling stations and the council sought to contact as many affected voters as possible.
Ms Baxter finished fourth in the result declared on 8 May.
She was 64 votes shy of third-placed Conservative candidate Norman Decent