It depends on whether the strike was a form of 'protected industrial action'. Although a strike, or other form of industrial action, is a breach of the contract of employment, which would normally give the employer the right to dismiss, the dismissal would be unfair if the action was 'protected'.
This would be the case where the action had been called lawfully, i.e. there had been a secret postal ballot, notice given to the employer, the balloting threshold was met, etc.; and where the strike is over a work dispute with your own employer. Workers who take 'unofficial' industrial action or engage in 'wildcat' strikes are not protected from dismissal. Check with your union if you are concerned at all about the legality of your planned industrial action.
Dismissal of employees engaged in protected industrial action is unfair:
If employees are locked out (i.e. prevented from returning to work) during the 12-week period, it will be extended (by one day for every day that the employee was locked out).
If you are in this position, take legal advice from a union rep as soon as possible. Deadlines for employment tribunals are extremely short.
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