Angela Rayner has demanded the Government 'get on' with leasehold reform as she warned any delay would be 'damaging'.
Marking the Prime Minister's card, his former deputy said that ministers should go 'further and harder' in tackling rogue managing agents.
It comes after she intervened to demand Sir Keir Starmer stick to his election pledge to cap ground rents.
Following her resignation last year, Ms Rayner - who is talked up as a future leader - has intervened on several occasions to force the Government's hand.
Appearing in front of the Commons Housing Committee, the former housing secretary called on ministers to stand up to those with 'vested interests'.
She said her message to the Treasury was to dismiss any attempts by freeholders to hold up the Leasehold and Freehold Reform Act passed by the last government.
'We know their appetite, but we also know that we can win the battle - and we should - and previous governments, including ours, have said "we've got to do it", so we should get on and do it,' she told MPs.
She added: 'And I think that too slow action on it will be damaging for us as a parliament, because it looks like the vested interests win over the will of the people.
'And quite frankly, it's not a political point. It's a right or wrong, and it's wrong what is happening, and therefore it's our duty to put it right.'
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She said the draft leasehold bill was 'some of the meatiest' legislation the Government was bringing forward but said 'of course it would be great to put more things within that bill'.
The government's draft leasehold bill is currently being scrutinised by the committee before making its way through Parliament.
It includes plans to cap ground rents - an annual fee leaseholders must pay to their freeholder - at £250 a year.
The legislation would also ban the sale of new leasehold flats and give homeowners greater control over how buildings are managed.
But it does not propose measures to regulate managing agents or to bring down increasing service charges.
Addressing this, Ms Rayner called on the Government to introduce an independent regulator and make service charges more transparent.
She told the MPs: 'I think the lack of regulation for management agents is a real problem.'
She added: 'We've for the mandate and we've got to move at pace.'
She said that proposals on the regulation around management agents needed 'to be taken forward'.
And she said she thought ministers should be doing 'more' to try to bring in the laws introduced by the last government.
Asked if she thought that real change could be brought about by the draft bill, Ms Rayner said: 'Yes, if they stick to it.'
Ms Rayner resigned as deputy prime minister, housing secretary and deputy Labour leader last September after failing to pay enough stamp duty on her flat.
She has since been said to be considering a run at the leadership, though must wait until she has resolved the issue with her flat with HMRC.
She has chosen key moments to intervene, forcing Sir Keir into a U-turn on his proposal to publish the Mandelson papers.