Neil Mitchell is threatening to sue Torex Retail for up to £30m after claiming he was unlawfully dismissed as chief executive of the software group last month.

In a letter to Steve Marshall, the interim chairman, Mr Mitchell said he would formally launch a claim for £5.4m for constructive dismissal in 28 days, saying that he had been unlawfully dismissed, after being suspended, in breach of his contractual rights. He told Mr Marshall he had not resigned. At the time, Torex said Mr Mitchell’s employment had been terminated and he had resigned.