Labour leader Sir Keir Starmer acts too much like a lawyer during public appearances and should "put some more welly" into speeches, according to his deputy Angela Rayner.
Ms Rayner emphasised how her boss was a funny character when there was "not a camera in his face" but public appearances often depict him as unemotional and cold.
Sir Keir's appearance at Prime Minister's Questions this week raised eyebrows, as he chose to narrow his attacks on the Government's track record on the NHS.
His comments follow Prime Minister Boris Johnson's biggest leadership challenge to date, when two in five Tory MPs voted to remove him from office.
Labour deputy leader Angela Rayner
Stefan Rousseau
Ms Rayner said: "I do think some of his conditioning when he was a lawyer and things like that, sometimes he takes the emotion out of it and he puts the strategic stuff in.
“And I think: ‘No, put some more welly into it!’”
Addressing the BBC podcast Newscast, Ms Rayner added: "I’ll go in with two boots — you know what I mean? Whereas Keir is a bit more sort of: ‘I’ll go in with the strategic case and the detail’.
“He cross-examines in a very forensic way, which I think some people prefer that style by the way. Other people think I’m too brash and I should tone myself down.”
Ms Rayner supported her boss, emphasising how he had a "good performance" but admitted she might have chosen to challenge the Prime Minister in a sterner manner had she been on the other side of the dispatch box.
“The way in which I’d have gone for Boris is probably slightly different to how Keir does it,” she added.
Keir Starmer and Angela Rayner
Stefan Rousseau
Ms Rayner admitted to being "very pro-industrial relations" when probed on whether or not she supported strike action across the rail network later this month.
Members of the Railway Maritime and Transport Workers (RMT) union will attempt to cause havoc across the network for three days in a dispute over pay and redundancies.
RMT have made a series of personal donations worth £5,700 to Ms Rayner, as the Labour leader has remained vocal in her stance to support workers in their strike action, attending protests and carrying placards.
She laid blame at the Government's door, defending the workers' right to strike.
The comments on Sir Keir's approach to the people arose in the wake of a focus group this week in the Red Wall constituency of Wakefield.
They suggested the Labour leader was failing to appeal to former Tory voters.
The focus group incorporated people who voted Conservative for the first time in 2019 and was conducted by Kekst CNC for Times Radio before the by-election on June 23.
Out of the eight voters, five said they would not vote Conservative again while Johnson was leader.
The voters said Starmer was a barrier to them returning to Labour, describing him as “weak”, a “slippery slimeball” and “someone who opposes for opposition’s sake”.