Union leaders have previously argued that walkouts by staff across multiple sectors would constitute a de facto general strike, the like of which has not been seen in the UK since 1926.

Only the Trade Union Congress (TUC) has the power to call a general strike, though its legality remains unclear after laws were tightened in the 80s.

The umbrella organisation which represents the majority of trade unions in the UK has a total of around 5.5million members.