The leader of the Unite union has said co-ordinated public sector industrial action on pay is "very likely".
Len McCluskey warned the Government that the union movement was prepared to take stronger action to oppose the wage cap on public workers.
He told BBC Radio Four's Today programme: "In terms of the concept of co-ordinated public service workers action, yes, I think that's very likely and very much on the cards."
Mr McCluskey is prepared to break the law to pursue public sector pay strikes, the programme reported.
The union leader said he was ready to defy a legal requirement that strike action needs to be approved by a ballot with a turnout of more than 50%, the broadcaster said.
He also floated the idea of the Labour Party having a second deputy leader who would be a woman.
Such a move is likely to be viewed as a thinly veiled attack on the party's current deputy chief Tom Watson, who has clashed with the Unite leader in the past.