Jeremy Corbyn has pledged to extend public ownership of the country's bus networks if he becomes prime minister.
The Labour leader, who is battling against challenger Owen Smith to retain his job, has said he will "rebuild and transform Britain's transport system".
He pledged to offer councils new franchising powers and allow them to set up local bus companies.
He also set out plans to bring railways back into public ownership to fix the present "transport nightmare".
Mr Smith's campaign said all of Mr Corbyn's proposals were already Labour policy.
The Labour leader promised to expand bus services to areas not currently covered, to give councils franchising powers over their bus networks, and to allow them to set up "municipal bus companies".
Mr Corbyn claims the moves would save money that could be used to reverse government cuts to local bus services.
Franchising powers are already to be expanded by the government's Bus Services Bill, focusing on areas with an elected mayor in place.
However, the bill, which focuses on services in England outside London, rules out allowing local authorities to set up bus companies.
The government says it will increase passenger numbers and "enable a thriving and innovative commercial bus sector".
Mr Corbyn also highlighted his flagship pledge to renationalise the railways - a pledge matched by Mr Smith.
Speaking at a protest about rail fares in London, Mr Corbyn pointed to the "pretty terrible service" run by Southern Rail in the South East of England, where passengers have held protests about train cancellations and timetable changes.
He said "pretty much everyone" agreed the Southern network should be publicly-run, adding that the current model was "not a sensible way of running a public railway system that we have all paid for".
Mr Smith's spokesman said his candidate would "go further" to improve transport with a £200bn infrastructure fund.
He added: "There is nothing new in what Jeremy is saying - he is simply rehashing existing Labour Party policy."
The winner of Labour's leadership contest will be announced on 24 September.
Mr Corbyn has won the backing of a majority of local constituency Labour parties (CLP) in his re-election bid, securing 285 CLP nominations to Mr Smith's 53, although the scorecard has no direct bearing on the result.
The leadership vote comes after Labour MPs signed a vote of no confidence in Mr Corbyn, who won an overwhelming victory among members in last summer's leadership contest.
Mr Corbyn said he was "looking forward to a good result" in the contest, adding that if he won he would appoint a shadow team "that represents all of the party".
Mr Smith, who has warned the "legacy of successive Labour governments" could be wiped out if the party continues along its current path, focused his campaign on the NHS on Monday.
He accused the government of having "a secret plan to privatise the NHS" in England - a view rejected by the Department of Health.
The two contenders will take part in a Labour leadership debate on the BBC's Victoria Derbyshire programme on Wednesday.