Sacked Labour frontbencher Sam Tarry this morning claimed it is "time to fight back" and "reclaim our party".
Mr Tarry was removed as shadow transport minister after giving media interviews at a picket line - sparking a massive backlash among the left of the party and unions.
In remarks that will ire leader Sir Keir Stramer, the MP said "people need to have a really hard think about what the Labour Party is for".
Speaking to a rally for striking BT workers this morning, he said Labour needs to be clear it would defend workers' rights to the hilt.
He called for leadership that "does not look the other way" when workers go to foodbanks.
The former shadow minister told members of the Communication Workers Union: "Let's be absolutely clear - it is not good enough, it is not good enough for the Labour Party to say that we probably won't be able to give you a pay rise in line with inflation.
"Because that means the Labour Party is committed to cut people's wages in real terms and that is totally unacceptable.
"If I'm sacked for having said that live on TV and not supposed to (have) been on that picket line then people need to have a really hard think about what the Labour Party is for.
"Because for me the clue is in the name: Labour. On the side of working people."
He added that "things were changing" and it was "time to fight back" and "reclaim our party".
Sir Keir has said he sacked Mr Tarry for booking himself onto media programmes without permission and making up policy "on the hoof".
Speaking during a visit to Birmingham on Thursday, the Labour leader said: "Sam Tarry was sacked because he booked himself onto media programmes without permission, and then made up policy on the hoof, and that can't be tolerated in any organisation because we've got collective responsibility.
"So that was relatively straightforward."
It is understood the policy Mr Tarry was considered to have fabricated was when he told Sky News every worker should get a pay rise in line with inflation.
Jeremy Corbyn, the former Labour leader and now independent MP, and Labour former shadow chancellor John McDonnell were also on the CWU picket line.
Mr Corbyn told the PA news agency: "I think the duty of Labour MPs is to support its affiliates. And the CWU is an affiliated union, they've asked for our help and support and I'm here today."
Addressing the rally later, he added: "Our job is to unite everyone in this campaign for real social justice. It's called socialism, where you don't leave anyone behind."
Mr McDonnell told the PA press agency: "These workers are being forced to take industrial action. I'm a Labour MP so I'm a member of the Labour trade union.
"When the call comes out from CWU for solidarity to join the picket lines, of course I respond positively."
He added: "If you're a Labour MP, whether on the frontbench or the backbench, you should be on the picket lines."
