The creation of the UK’s largest private sector union has been delayed after a pensioner from north London lodged a complaint.

A merger between Amicus and Unifi was announced on Tuesday, but officials revealed yesterday that the certification officer had been been unable to approve it because of the last-minute complaint.

The complainant, a Unifi member and former NatWest banker, is understood to have attacked the way Unifi members were balloted on the merger.