Park Place, Croydon's proposed new £500m shopping centre, has been dragged into the loans for peerages row which has rocked the Government.
Reports have suggested that Deputy Prime Minister John Prescott granted Minerva, founded by two developers who lent large sums of money to the Labour Party, planning permission for the centre in return for the loans.
Mr Prescott, who called it "a lie", dismissed the suggestion, but Croydon Conservatives are calling for an inquiry.
Minerva's founders, Sir David Garrard and Andrew Rosenfeld, loaned Labour £3.3m. The Government has come under intense criticism in recent weeks after Labour officials admitted to receiving loans from businessmen who have since gone on to receive peerages.
Sir David and Mr Rosenfeld are also involved in an investigation into the collapse of Allders last year. At the time Allders was owned by Scarlett Retail, whose largest shareholder was Minerva, which had a 60 per cent stake.
Minerva said it was "ridiculous" to suggest the loans were linked to planning permission for Park Place being granted.
Salmaan Hasan, Minerva chief executive, said: "There were no corruptive influences involved. I find the suggestion of that ridiculous."
Croydon Council has not hidden its desire to see the shopping centre built. A rival scheme, Bishops Court, was refused planning permission.
The Minerva's paid council legal fees for a subsequent public inquiry into the Bishops Court plan, but denied any wrongdoing.
A spokesman for the Office of the Deputy Prime Minister said: "Mr Prescott did not grant planning permission to Minerva. It was done by Croydon Council."
Councillor Mike Fisher, Croydon Conservative leader, wants no more planning decisions affecting the Park Place development to be taken until an inquiry into the revelations is conducted.
The shadow council leader said: "I think these allegations create cause for concern with regards to the Park Place development and questions need to be answered about whether or not the original decisions were made appropriately.
"The council should hold off making other planning decisions regarding Park Place until an inquiry takes place. We've always supported Park Place and see it as a positive move, but we do have concerns over whether or not such a large centre is sustainable. We don't want a half-empty shopping centre."
Croydon Council has taken full responsibility for granting planning permission for the Park Place development after Mr Prescott declined to use his power to call in' the planning application for review.
Phillip Goodwin, the council's director for planning and transportation, said: "The Secretary of State declined to call in the application and left decision-making entirely in the hands of Croydon Council. The planning process, as always, was conducted openly, transparently and quite properly.
"We expect the Park Place development to bring substantial benefits to the town centre and for the scheme to act as a major catalyst in realising more of the ambitions set out in the council's Vision 2020."