However, the Scottish government recently committed to introducing long-term measures to cap rents.
Campaigners said the likelihood of a Labour victory in the general election should see Khan work with Keir Starmer to establish a Rent Control Commission to introduce rent controls across London.
“Sadiq Khan’s new deal will fall flat if he does not continue to push for the power to cap rents in London,” said a London Renters Union spokesperson.
“London renters are trapped in a cycle of instability and many will feel let down if Khan stops campaigning for city-wide rent controls under a Labour government. Six thousand new rent controlled properties will not bring security to the capital’s three million private renters who are living in fear that they will be forced out of their homes by an unaffordable rent increase.
“A third term offers Khan a once-in-a-generation opportunity to push a likely new Labour government and bring much-needed rent control to the capital.”
As well as building the rent control homes by 2030, Sadiq Khan’s manifesto for the 2 May election also includes plans to invest in support to help renters defend their rights, with advice, guidance and funding for groups such as renters’ unions.
He has promised to freeze City Hall funding for landlords whose properties fail to hit housing standards.
Khan accused Tory rival Susan Hall of being “in the pockets of the landlord lobby” and being silent on renters issues on the campaigning trail.
“This election is a close two-horse race and the choice is clear – someone who will introduce rent control homes and stand up for renters, or the Conservative candidate for mayor who has been virtually silent on renters’ issues and stands with the Tories on the side of the landlord lobby,” said Khan.
“I’ll be a renters’ champion in City Hall and work together with a future Labour government to deliver a new deal for renters across London.”
Khan has recently been on a collision course with the Conservative government over his housing plans.
Housing secretary Michael Gove wrote to Khan to launch a review into his London Plan, citing “chronic under-delivery” and the need to boost brownfield development.
Khan said last May that he had started to build more than double the amount of council homes in the rest of England combined. Last month he promised to build 40,000 new council homes by the end of the decade.
Tory mayoral candidate Hall has promised to build more family sized homes and vowed not to build tower blocks.
Hall said: “If Sadiq has been able to do this the whole time, why is he just announcing it now? Rent controls have never worked, and Sadiq knows it.
“His hair-brained plan would worsen the housing crisis for Londoners and shows he simply isn’t listening.
“I am listening to Londoners, and that’s why I would build more family sized homes, to increase supply – and therefore bring down rents.”