How long must an employee work before claiming unfair dismissal in the UK?

The ordinary unfair dismissal right requires two years of continuous employment. Certain dismissals are automatically unfair from day one, including dismissal for pregnancy, for whistleblowing, for asserting a statutory right or for trade union reasons, and those need no qualifying period. A claim is normally brought within three months less one day of the effective date of termination, after early conciliation through Acas.