A former aide to Boris Johnson advised him on new planning laws while being employed by two major property firms, a report claims.
Industry insiders told the Mirror that Eddie Lister, who stepped down from No 10 over a conflict of interest, had been advising on the proposals.
Whitehall sources suggested that Lord Udny-Lister had been involved as the Downing Street policy team drew up the plans with Robert Jenrick’s Ministry of Housing last year.
The peer has previously admitted he had “a couple of other bits and pieces” of work while he was in government but argued there were no conflicts of interest and all had been declared.
The radical planning laws, now approved by Johnson, will overhaul rules that slow down or obstruct house building and force councils in England to dedicate land to development or preservation.
One development industry insider said: “Eddie was involved in the evolution of planning policy that was announced in Jenrick’s white paper.
“It was a wholly untenable position in light of the conflicts of interest.”
Lord Udny-Lister was an adviser to property group Delancey and a non-executive director to Stanhope Holdings during his time at No 10.
The Tory peer admitted he had attended several meetings where the planning changes had been discussed – but denied he was a key architect of the plans.
He told the Mirror: “I was in various meetings where the subject came up. I was never part of the detailed work on this.
“It was mainly done by the No 10 policy team and MHCLG. My hands are well away from this one.”
But shadow communities secretary Steve Reed said: “The Conservatives are giving developers more control over planning and gagging communities so local people lose the right to object.
“We need to know urgently what role Lord Lister played, given the conflicts of interest now coming to light in his relationships with wealthy developers who donate increasing vast sums of money to the Conservative Party.”
Labour has written to cabinet secretary Simon Case to ask him to look into any potential conflict between Lord Lister’s public and private roles.