Sir Keir Starmer said he sacked former shadow minister Sam Tarry for making up policy “on the hoof,” as he struggled to contain a row with the unions and the left-wing of his party over the move.

The Labour leader fired Mr Tarry from his role as a shadow transport minister after he gave a round of broadcast interviews from the picket line that were unauthorised by party headquarters.

Speaking during a visit to Birmingham on Thursday, Sir Keir 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.”

He added: “The Labour Party will always be on the side of working people, but we need collective responsibility, as any organisation does.”

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.

Asked if shadow ministers would be allowed to join picket lines in upcoming strikes if they did not make any unauthorised media appearances, Sir Keir said: “We take each case as it comes.

“My criticism is really of the Government because it’s inevitable, I think, when you’ve got a cost-of-living crisis, that so many working people are concerned about their wages. I understand that, I understand the concerns.”

Labour has not officially supported the industrial action, but has accused the Government of inaction and urged ministers to get involved in negotiations.

Mr Tarry’s sacking was met with fury by unions and the left-wing of the party.

Labour former shadow chancellor John McDonnell described it as a “severe mistake”, accused Sir Keir of “misreading the mood of the public” and backed calls for a general strike.

“This is a completely unnecessary row that’s been invented just at a time when the Tories are tearing themselves apart, and we’ve got the maximum opportunity I think to gain an advantage in the polls that will build the support to take us into a government,” the MP for Hayes and Harlington told Sky News.

“This is an unnecessary dispute and whoever has advised Keir Starmer on this, I think he has made a severe mistake.”

He added: “I think they’ve misread the mood within the labour and trade union movement. But I also think they have misread the mood amongst the general public.”

Asked about the general strike proposed by RMT general secretary Mick Lynch, the former shadow minister said he said he supported “co-ordinated action”.

Sir Keir said it was “quite right” for trade unions to “stick up for their members” when he was asked whether he would agree with a general strike if Liz Truss goes through with her pledge to crack down on the unions should she become prime minister.

Calling Ms Truss’s policy “completely wrong”, the Labour leader told reporters: “Of course, trade unions are right to stick up for support and negotiate on behalf of their members. I’m fully supportive of that, working with our trade unions.”

The firing of Mr Tarry, who is in a relationship with deputy Labour leader Angela Rayner, drew condemnation from unions, Labour MPs and other party figures.

Andy Burnham, the Labour mayor of Greater Manchester, warned that the party needs to be “careful” that it does not end up undermining working people “fighting to protect their incomes”.

He told GB News: “Labour needs to be careful here. We can’t ever be a party that undermines working people fighting to protect their incomes and a cost-of-living crisis.

“If we’re not careful, that’s how we might come over.”

MP for York Central Rachael Maskell called for the Labour leader to visit picket lines on Wednesday night, while GMB general secretary Gary Smith said it was a “huge own goal” for Labour to “turn a Tory transport crisis into a Labour story”.

Transport Salaried Staffs’ Association (TSSA) general secretary Manuel Cortes, RMT boss Mr Lynch and Unite general secretary Sharon Graham all criticised Sir Keir’s decision.

Mr Tarry is a former official of the TSSA rail union.

Asked if he is worried about the prospect of the Unite union withdrawing their funding from the Labour Party, Sir Keir said the relationship between the two “is historic, it is present, and it will be the future of the Labour Party”.

In a statement, Mr Tarry said it had been a “privilege” to serve on Labour’s top team.

“I remain committed to supporting the striking rail workers, and campaigning for a Labour victory at the next general election, which I will fight for relentlessly from the backbenches,” he said.

Rail passengers suffered fresh travel chaos on Wednesday after thousands of workers walked out on strike, crippling services across the country.