Anas Sarwar says the Prime Minister has “found his heart, found his fight” at the Labour conference.
The Scottish Labour leader defended Sir Keir Starmer but said his party must “shout louder” rather than “whisper” about its achievements.
Mr Sarwar joined Defence Secretary John Healey on a visit to the Malin Group’s welding skills centre in Glasgow on Wednesday.
The Ministry of Defence provided funding to the centre, which will be operated by Rolls-Royce and support naval shipbuilding in Scotland.
Mr Healey has accused the Scottish Government of failing to back the centre due to the SNP’s “anti-defence stance”.
Speaking to the PA news agency, Mr Sarwar said Sir Keir had found his confidence at the conference in Liverpool.
He said: “He’s found his confidence, he’s found his heart, he’s found his fight, he knows what he’s against.
“He knows the kind of country he wants to build.
“My challenge is we don’t need to just hear that in five days of a Labour conference – I want to hear the Labour case, I want to hear the Labour achievements and I want to hear about Labour choices every single day so we can defeat both Reform and the SNP.”
Pressed on whether he was happy with Labour right now, Mr Sarwar said: “Even when we have done good big things, we whisper them.
“We don’t tell people what’s happening, and we can’t allow our opponents to deliver the message for us.”
He said the party should be “shouting louder” about achievements such as cuts to mortgage rates and increasing wages.
The Prime Minister should be talking about these achievements “every single day”, the Scottish Labour leader said.
Mr Sarwar also attacked Reform UK leader Nigel Farage, mocking him as a “snowflake” who is unfit for public office.
The Scottish Labour leader said: “Poor Nigel, so thin-skinned, such a snowflake, feel so sad for him.
“The reality is the man is not fit to be in public office, he’s not fit to lead a political party and he’s not fit to run this country.
“Obviously I’ll always be more Scottish than Nigel will be but what makes me different from Nigel is I want to bring my country together.
“He wants to divide it, and Scotland will reject him.”
Mr Healey also defended the Prime Minister’s position, saying: “Keir Starmer’s position is and always has been strong.
“It’s even stronger now after the Labour conference.
“What you saw from him was someone who is a leader that is passionate, determined, proud to lead Labour in government.
“But above all, determined to see the renewal of the UK after 14 years of austerity and failure from the Conservative government.”
