Thousands of ballot papers could be declared null and void due to human and printing errors.

A mismatch of identification numbers in the ballot pack has occurred on papers sent out from at least three constituencies and could leave thousands of voters disenfranchised.

The three constituencies, which have not been named, could face legal challenges from candidates if the results are close, or from individuals who have been unable to cast a vote.

Returning officer chiefs predicted that more cases would follow in other constituencies as voters opened ballot papers and discovered the errors.

But they advised election officers against reissuing ballot papers, which they suggested could lead to further chaos.