Jeremy Corbyn claimed that he was in charge of a “strong shadow cabinet” only for another senior member of his team quit just hours later on Monday morning.
Catherine McKinnell has stepped down as shadow attorney-general — the first resignation from the shadow cabinet since Mr Corbyn became leader last September.
The move followed resignations last week by three more junior members of Labour’s front bench team: Kevan Jones, Jonathan Reynolds and Stephen Doughty.
Ms McKinnell said in a letter to the Labour leader that it had become “increasingly difficult not to speak up in the Commons” about issues on which she disagreed with him.
“As events have unfolded over recent weeks, my concerns about the direction and internal conflict within the Labour party have only grown,” she wrote. “I fear this is taking us down an increasingly negative path. I feel that I would like to channel my energy constructively, into making positive changes for my constituents.”
Earlier Mr Corbyn said he believed he had a “strong shadow cabinet” after last week’s protracted reshuffle, as he attempted to get back on to the front foot ahead of elections in May.
Mr Corbyn claimed to be ignorant of briefings by his team that Hilary Benn, shadow foreign secretary, was being lined up for the sack; in the end Mr Corbyn did not move him.
“I don’t know where the briefings came from,” he told the BBC, insisting that while Mr Benn might disagree with him on some issues he felt he would be able to develop “a human rights-based foreign policy”.
Asked whether, as prime minister, he would be prepared to authorise a drone strike on a leading Isis militant, he said it was a “hypothetical question” and that he would want to see the evidence first.
Mr Corbyn said he would want to find out what difference it would make and whether it might be possible to capture the militant, but accepted that “action could be taken”.
Meanwhile, the Labour leader urged Jeremy Hunt, health secretary, to hold urgent talks with junior doctors who are planning industrial action.
He also said he supported a CND rally planned for next month to protest against the renewal of the Trident nuclear weapons system. But he added that he had not been invited to attend.
Trident is a highly divisive issue in the Labour party: Mr Benn is one of those strongly in favour of retaining it.
Mr Corbyn said that he wanted to give party members a say in developing Labour policy, including a greater role for the party’s annual conference.
Meanwhile, senior Labour figures have voiced concerns about the impact on the party’s finances of the government’s trade union bill, which has its second reading in the House of Lords tonight.
Labour could lose as much as £6m a year as a result of the government’s proposals, which include forcing union members to “opt in” to political funds rather than “opt out” under the current system.