A strike is defined in TULRCA 1992 as "any concerted stoppage of work" (TULRCA 1992, s.246). This can include an overtime ban or a rest-day working ban called by a trade union (see Connex SE v RMT Union CA 1999 IRLR 249, CA).

The Employment Relations Act 1999 sch.3 para 6(2) provides that for the purposes of the new rules on ballots authorising industrial action an overtime or call-out ban shall count as "industrial action short of a strike".

There is no statutory definition, as such, of "official industrial action" or "official strike". However, there is a kind of definition, more of a description than a definition, of "unofficial strike" and "unofficial industrial action". Any strike or other industrial action which is not authorised or endorsed by a trade union will generally be "unofficial" (TULRCA 1992, s.237(2)).

An employee taking part in unofficial industrial action at the time he is dismissed is normally disbarred from making any unfair dismissal claim (TULRCA 1992, s.237). He will be able to make such a claim only if he was dismissed for one of the "automatically unfair" reasons specified in TULRCA 1992, s.237(1A) such as dismissal in family, health & safety, working time, employee representative and whistleblowing cases.

Individuals who take part in official industrial action have been given increased protection against dismissal since 24th April 2000 when Employment Relations Act 1999 s.16 and Employment Relations Act 1999 sch.5 came into force (see the Employment Relations Act 1999 (Commencement No. 5 and Transitional Provision) Order 2000, SI 2000/875 and 2000/03/24 - DTI press release P/2000/209, New measures to encourage both parties to resolve differences unveiled.

The general effect is that the dismissal of an employee for taking lawfully organised, official industrial action is automatically unfair dismissal if:

- it takes place within twelve weeks (8 weeks until 6th April 2005) of the employee commencing industrial action; or
- it occurs after this 12 week period but the employee had returned to work before the end of the 12 weeks; or
- it occurs after this period and the employer has not taken all reasonable steps to resolve the dispute.

See also Trade union matters/industrial action and/or Strikes/a general note and/or Unfair dismissal/automatically unfair dismissals/industrial action .