Housing Secretary Robert Jenrick still has questions to answer over his role in a planning case involving a Tory donor, Sir Keir Starmer has said.
The Labour leader told the BBC the matter was "far from closed" but stopped short of calling for the minister's resignation.
Mr Jenrick is under fire after granting permission for a luxury housing development to donor Richard Desmond.
Downing Street said the PM had full confidence in the minister.
Mr Jenrick says he was motivated by a desire to see more homes built when he overruled government inspectors to give the green light to Mr Desmond's plans for a 1,500 home development at the former Westferry printing works, in London's Isle of Dogs.
Twelve days after the decision Mr Desmond, the former owner of the Daily Express, gave £12,000 to the Conservative Party. Mr Jenrick said he had no knowledge of the donation and had acted on the "merits" of the case throughout.
On Wednesday, Downing Street said Boris Johnson now considered the matter "closed" after Mr Jenrick published details of his contacts with Mr Desmond.
But Sir Keir Starmer told the BBC's political editor Laura Kuenssberg: "We want straight answers on this, and I think the public do, they can tell that something's wrong here."
He added there were "discrepancies" between the documents published by Mr Jenrick and the account of events he gave to MPs on Wednesday.
He said the matter was now at the stage "where the prime minister's judgement is an issue".
He renewed calls for the UK's top civil servant Sir Mark Sedwill - who has said he is satisfied with Mr Jenrick's account of events - to investigate whether he broke the guidelines for ministerial conduct.
On Thursday the PM's spokesman said No 10 had had "no involvement" in Mr Jenrick's decision to green-light the scheme.
Labour has written to Mr Jenrick demanding he publish additional documents beyond those he released on Wednesday.
Mr Jenrick had said he would use the Freedom of Information Act as a "benchmark" to release "all relevant information" about the planning application.
In a letter, Labour's shadow communities secretary Steve Reed called for him to publish documents beyond the scope of the Act "in the interests of transparency".
A billionaire with a planning problem finds himself sitting next to the cabinet minister responsible for planning, at a Conservative fundraising dinner.
The two later exchange texts and planning permission is granted in the nick of time, just before the developer would have found himself on the hook for a whopping tax bill.
The billionaire then makes a donation - albeit a small one - to the Conservative Party.
Little wonder this has caused Labour and others to ask loads of questions about what on earth was going on.
It looks bad. That's not my judgement - but that of Robert Jenrick.
Mr Jenrick changed his mind and rescinded the planning permission, as it was "unlawful by reason of apparent bias".
Note the word "apparent."
The minister insists he wasn't biased, he declined to visit the proposed building site, and he has always been committed to and driven by ensuring more houses are built.
Oh, and there is still no permission for the building work to start.
Notably, Labour is not calling for Robert Jenrick to resign and the prime minister says the case is closed.
So, for now at least, Mr Jenrick appears safe.
Mr Desmond had been lobbying for the proposed 1,500-home development to be approved before the local council, Tower Hamlets, introduced a new Community Infrastructure Levy (CIL) to pay for local services.
In a text message to Mr Jenrick in November 2019, with an apparent reference to the Labour council, Mr Desmond wrote: "...we appreciate the speed as we don't want to give Marxists a load of doe [sic] for nothing!"
In one of the papers, a civil servant wrote, "On timing, my understanding is that the SoS is/was insistent that the decision issued this week i.e. tomorrow - as next week the viability of the scheme is impacted by the change in London CIL."
Mr Jenrick approved the scheme on 14 January, by which Mr Desmond avoided paying £40 million for the levy.
Business Minister Nahim Zahawi said Mr Jenrick had been motivated by a "getting stuff built".
"But when there was a perception of bias, he pulled back on this, pulled the plug on it and will now allow a different minister to decide the scheme. The access didn't buy this billionaire a decision."
John Biggs, Labour mayor of Tower Hamlets said: ''The revelations about the Westferry printworks decision have blown apart confidence in our planning system under Mr Jenrick.
"The documents he was forced to release are damning and it looks like he rushed through the decision to help save the developer money and short-change my residents.
''The Minister referred to our borough as 'rotten', and messages from the developer called our council 'Marxist'.
"This name calling says more about them and their disregard for my residents whose borough it is, and who rightly want much needed affordable homes and money for local services.''
Speaking on Wednesday before the documents were released, Mr Jenrick said the accusations were "not simply wrong but actually outrageous", adding the decision had been made on its merits after a thorough process.
But he admitted "things could and should have been done differently", saying: "On reflection, I should have handled the communication differently."