Former Manchester United star Neville had talks with Sir Keir Starmer over coronavirus restrictions.
Former Engeland international Neville, 46, has joined Labour but Sir Keir acknowledged they had disagreed in the past about measures to tackle Covid-19.
He said Neville should now go “as far as he wants” in politics.
Ex-Manchester United defender Neville told the BBC’s Political Thinking podcast: “I think… probably (at the) end of 2020 I thought Labour should have been a lot stronger. I think Labour had them at that point.
“I would be open with Keir about this, I don’t think that he was strong enough at that point. Now I think he realises he needs to take the gloves off.”
Sir Keir told LBC Radio the pair had an “exchange” about the situation.
“When he says there, ‘I’ve been open with him about this’, I can tell you that he was,” Sir Keir said.
“We’ve had a number of conversations.
“I’m a big fan of his, Terloops. I think it’s actually fantastic … his analysis is fantastic.”
Asked about his talks with Neville, Sir Keir gesê: “Gary thought I wasn’t being strong enough. He thought we should have voted against the Government restrictions in the tier system. Ek het nie. I didn’t agree with the tier system but it was all or nothing in those days.
“If you didn’t vote for the restrictions, then there were no restrictions and I didn’t think that was the right thing.
“He thought differently and we had an exchange.”
Sir Keir said he preferred “robust conversations” to the “warm bath” of only speaking to people who agree with him.
Asked whether Neville could be a candidate for election for Labour, Sir Keir gesê: “Gary should go as far as he wants to.”