Jeremy Corbyn has all the qualities he needs not just to lead the Labour Party but to be prime minster, according to another left-wing veteran of Labour’s internal battles.

Ken Livingstone was once the most renowned, or notorious figure on the Labour left. Ostracised by Tony Blair, he confounded the party machine by running for the office of London Mayor in 2000 as an independent – and winning famously. If he could win London, his old friend and fellow socialist can win in the country, he claims.

But he fears that the Tories may have found their own “Jeremy Corbyn” in Zac Goldsmith, the independent-minded Tory MP who is expected to be their candidate in next year’s London mayoral election.

Livingstone declared back in May that he believed that the former transport minister Sadiq Khan would be Labour’s best candidate for London Mayor. At the time, he emphasised Khan’s experience of government office as a strong point in his favour.

But that was before Jeremy Corbyn, who has never held any kind of office in 32 years as an MP, put himself forward as a potential prime minister in waiting. Now, as Livingstone hopes his old friend will storm to victory, he is not so sure that experience of high office is an essential requirement for a winning candidate. He claims that Corbyn’s record as an outsider who never sought preferment is the very quality that will bring back Labour’s lost vote.

“People who defected to Ukip are never going to think Jeremy’s just part of the Westminster establishment,” he said. “He hasn’t got half a dozen houses. He hasn’t raked in millions of pounds. He’s not getting bungs from some corporation.

“Jeremy has been completely embedded in serving his constituency. He’s completely in touch with how tough life is for ordinary people.”

Others have suggested that Corbyn is too left wing to appeal to a broad electorate, and too old at 66 to pick up the managerial and communication skills that the leader of a major party needs. But Livingstone, who has known Labour’s putative leader since they were newly elected councillors plotting to take the London Labour Party off to the left in the early 1970s, claims Corbyn’s age and his lifelong policy of saying what he thinks are the assets that will bring him electoral success.

He adds that Corbyn is the “nicest person in politics” – a quality that will help him win swing voters in a general election just as it worked for John Major in 1992.

Men in their forties are too anxious to prove themselves, he argues, but Corbyn’s age has given him solid confidence in himself and his beliefs. Livingstone denies that he is to be compared with that other elderly Labour leader, Michael Foot, who led the party to electoral catastrophe in 1983, and was much ridiculed for appearing at a solemn wreath-laying ceremony at the Cenotaph wearing what looked like a donkey jacket.

Corbyn has an aversion to wearing ties and is the several times winner of the Worst Dressed MP award, but Livingstone believes he has enough judgement to know when to look smart, while his general habit of dressing down is part of his appeal. “Most people don’t wander around dressed like members of the House of Commons,” he said. “Jeremy would wear a suit and tie for the Cenotaph.”

He also believes that there is a way round the problem of the threadbare support that Corbyn has among Labour MPs. Fewer than one in 10 wanted him as their leader, and those who did not are asking why they should be expected to show loyalty to someone who was a serial rebel under previous leaders.

The Livingstone solution is for Corbyn to tell the troops how they are expected to vote, using the normal procedure of notices issued through the whips’ office, but should not try to sanction MPs who defy the whip. Instead, he should leave it to the hundreds of new members who have joined Labour since the election, most of whom are believed to be Corbyn supporters, to call MPs to account if they fail to back their new leader.

He says that worked when he was leader of the Greater London Council in the 1980s, and Labour had a majority of four that included eight councillors as vehemently opposed to Livingstone as Blairite MPs are to Corbyn.

“The rigid discipline that was imposed under Tony Blair just encouraged rebellions,” Livingstone said. “The moment you’re told by some whip in some nasty manner to vote for something, you’re tempted to tell them to bugger off. We found that if councillors were told they were always free to oppose group policy, the rebellions just folded.

“If MPs vote against the whip, let them sort that out with their new party members. That would certainly work.”

The ex-Mayor is scathing about the record of his successor, Boris Johnson, accusing him of having used his eight years in office “to promote Boris”. But Livingstone said he had not intended to get involved in the issue of who should be Labour’s candidate in the 2016 election, until he he saw that the eventual line up could be Zac Goldsmith versus the former Culture Secretary Tessa Jowell, an election he fears Goldsmith might win.

“He is very dangerous to Labour,” he says of Goldsmith. “He’s a bit like Corbyn – he says what he thinks. He came on LBC and was the best of the Tory MPs we have had on. He’s very relaxed. He’s not after a government job. That’s what Londoners like.”

But as he explains why he came out for Sadiq Khan as the man to beat Goldsmith, he seems to contradict everything he has said earlier about Jeremy Corbyn.

“Tessa wouldn’t be a bad mayor. Sadiq is just more energetic,” he said. “He just comes over as more normal. Tessa is very cool and relaxed and all that. Londoners want someone manic.”

So, Londoners will vote for a “manic” mayor while the country as a whole will go for a nice guy in his sixties who will be so relaxed that he will not even try to force MPs from his own party to support him on key votes. Such a take would sound idiosyncratic, even naive, if it didn’t come from someone who has been in the hothouse of London and national politics for an extraordinarily long time.

As the leader of the GLC, Livingstone was a household name before Tony Blair was an MP and while David Cameron was still at Eton. He had 14 frustrating and barren years as a backbench Labour MP until he grabbed a second bout of fame and notoriety as a directly elected mayor.