Senior Labour MP John McDonnell says he supports a general strike and criticised Sir Keir Starmer for sacking a junior minister after he stood on the picket line during yesterday's rail strike.
He told Sky News that Labour leader Sir Keir has "misread the public mood" by failing to have specific targets on what workers should be paid and questioned who is advising him.
The Labour stalwart also said the party should be supporting the strikes and there should be a general strike if no progress is made.
The last time a general strike - where workers of different industries coordinate strike action - took place was in 1926 and was the only one that has ever taken place in the UK.
Mr McDonnell told Sky News' Kay Burley: "I support coordinated action because if that results in a decent pay rise for people that protect against the cost of living crisis, I think that's the most effective thing to do.
"But this is completely unnecessary, what it needs is the government to recognise you can't expect people to have to stand to one side when their wages have been cut."
He added that he has "never seen this level of anger but also this level of solidarity, wave after wave of trade unions".
There have already been, or will be, strikes by Post Office workers, rail, tram and bus workers, bin lorry workers, airline and BT Broadband staff this summer.
Mick Lynch, head of the Rail, Maritime and Transport (RMT) union, called on Wednesday for a general strike in retaliation to the government's threat to curb industrial action, warning of "the biggest resistance mounted by the entire trade union movement".
Simon Weller, assistant general secretary of the ASLEF union, told Sky News they have not discussed coordinated action but predicted it would be a "summer of solidarity" by workers.
Tory leadership candidate Liz Truss called the strikes "militant action" and promised to push through laws to make sure "essential services are provided on our railways" if unions strike, if she becomes prime minister.
'Severe mistake' to sack Labour MP on picket line
Mr McDonnell also said he supported Sam Tarry, who is Labour deputy leader Angela Rayner's partner, after he was sacked from his junior transport minister position on Wednesday after he appeared on the picket line at Euston Station and said workers should be getting a pay rise in line with inflation, which is set to rise to above 11%.
The Labour Party said Mr Tarry was sacked for doing broadcast interviews, including with Sky News, from the picket line and is understood to have been told it was because he said it was "not acceptable to offer below inflation pay rises" as it would be a real-terms pay cut for workers.
Labour's official position has been to call for ministers and unions to negotiate terms. They had also said ministers should not join picket lines.
Mr McDonnell said it was a "severe mistake" to sack a Labour MP for being on a picket line, adding that the party was formed by the trade unions "so when the trade unions have a just cause, we support them - and this is a just cause".
Some in the party believe Mr Tarry was goading Sir Keir into sacking him to help him fight a deselection battle.
Wards in Tarry's Ilford South constituency unanimously voted for a full reselection, meaning he is likely to lose his seat.
Mr Tarry won the east London seat in 2019 after local council leader Jas Athwal, who was also going to run, was suspended from the party just before the vote over allegations of inappropriate behaviour.
Mr Athwal was subsequently cleared after an almost year-long internal investigation but has spoken of how it badly affected him.