More than 1 million public sector workers are to vote on strike action in the biggest-ever union industrial action ballot.

The Unison union said probation officers, nurses, social workers, teaching assistants, school kitchen assistants and hospital cleaners would be among those voting in the row over public sector pensions.

The result of the ballot will be known on 3 November, giving time for Unison to strike on the TUC day of action, which takes place on 30 November.