The unions has accused ministers of refusing to negotiate over its economic and social policies.
Unite General secretary Len McCluskey said:
Our members at HCA are showing solidarity with their HCA colleagues in PCS against the savage attack by the coalition on public services and those dedicated staff that deliver them.
The anger is growing at the negative dead end economic and social policies of this right-wing government - from the easy ride that the City elite receives from George Osborne to the gross unfairness of the hated bedroom tax which will hit 650,000 people.
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Shadow business secretary Rebecca Long-Bailey has called for "immediate" relief to prevent thousands of companies going out of business.
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Those taking part in the bizarre trend say the combination of fruit juices and hot water makes for a uniquely liberating experience.