Shadow defence secretary Emily Thornberry has been branded "waffly and incoherent" amid renewed Labour infighting over Trident.
Mrs Thornberry gave a presentation on her approach towards the issue of renewing the nuclear deterrent at a meeting of the Parliamentary Party.
Leader Jeremy Corbyn has been accused of appointing her to the key job because she shares his support for unilateral disarmament.
After Mrs Thornberry's appearance on Monday evening, former shadow defence minister Kevan Jones said she had taken questions "but didn't answer any".
"Waffly and incoherent," he told reporters outside.
Mrs Thornberry, who spoke for around half an hour, said she wanted to carry out the ongoing review of Labour policy on Trident in an "atmosphere of mutual trust and respect".
In the face of hostile questions from MPs and peers, she said: "There is no point trying to shout me down."
Some MPs complained that she had compared the Trident system to Spitfire aircraft.
However, a senior Labour source insisted she had been trying to suggest that some military technology had to be replaced, like Spitfires, and others could be updated - like Tornadoes.
The source indicated that Mrs Thornberry had also raised doubts about whether submarines were a safe way to carry the nuclear deterrent.
"She was talking to some people about drones and it was apparent it was absolutely possible that large submarines could be tracked and attacked by drones," the source added.
Interventions were "evenly" split between speakers who wanted to renew Trident, those who did not think it was a "binary choice", and those who opposed renewal, according to the source.
Quizzed on how it had gone as she left the meeting, Mrs Thornberry said: "Alright."
When former leader Lord Kinnock was asked for his verdict he replied, "Yeah", and then walked away laughing.
Mr Corbyn was not present as he was manning a phone bank for Labour's London mayoral candidate Sadiq Khan.
However, he is expected to attend the next PLP meeting in two weeks' time.