The practice pushes up the cost of the final project by forcing developers to squeeze more onto a site in order to turn a profit. In some countries, such as Canada and Germany, it is regulated against by authorities requiring a planning permit be renegotiated if a property is sold. The highest-profile example in Melbourne is 555 Collins Street, over which the city council will on Tuesday ask Mr Guy to reverse planning laws he changed last year. In April 2013 Mr Guy altered the planning rules on the site, owned at the time by developer Harry Stamoulis, to allow a tower on it to overshadow the south bank of the Yarra River. Mr Stamoulis bought the property for $38 million in 2003. Soon after Mr Guy changed the planning rules for the site, he sold it to Singaporean developer Fragrance Group for $78 million.

Mr Stamoulis declined to comment on his Liberal Party links when contacted on Tuesday. In 1999, he helped Nicholas Kotsiras, the outgoing member for Bulleen, win preselection for the seat. Mr Kotsiras will be replaced in Bulleen by Mr Guy at this month's election. The Collins Street property is just one in a series of properties traded soon after getting the nod from Mr Guy. Fairfax Media has identified six others either successfully sold for huge profits after getting planning approval from Mr Guy, or put on the market almost immediately after gaining planning permission for a tower. Melbourne City Council's deputy planning chairman, Stephen Mayne, said Mr Guy's decision to allow a building at 555 Collins Street to overshadow the Yarra River was "the most confounding and perplexing we've seen by the minister".

"It came out of the blue, and there was no tradeoff public benefits for allowing huge overshadowing of the south bank of the Yarra River," he said. "The minister has never explained this decision. There deserves to be a serious look at who spoke to who, who promised what, and why this was done," he said. Cr Mayne compared the decision on 555 Collins Street to Mr Guy's refusal of a tower on the next Collins Street corner up – at the corner of Williams Street – where building industry super fund CBUS wanted to build a similar height skyscraper. Asked if the shadow controls for the site he approved last year should now be removed, Mr Guy's spokesman said there was no building approved on the site. And he said the CBUS tower had been rejected due to "considerable design issues" as well as overshadowing.