His council recently became aware that a 77-storey tower proposed for the former Carlton and United Breweries site would result in the popular public plaza being cast in shadow for hours during winter.

But their battle is unlikely to be straightforward, because of a tricky discrepancy in Melbourne’s planning scheme.

Clause 22.02 of the scheme dictates that developments should not cast any additional shadows on the State Library forecourt between 11am and 2pm on June 22.

However in 2007 the Carlton Brewery Comprehensive Development Plan was also incorporated into the planning scheme by then Planning Minister Justin Madden, naming the preferred maximum height of a tower at the site on 156-172 Victoria Street at 302 metres.

A skyscraper this height would easily overshadow the library forecourt, creating a significant conflict in the planning scheme.

Cr Doyle has argued for the original rules protecting the forecourt to stand. It is his belief that the State Library plaza is one of the rare “sacrosanct” public spaces in the planning scheme, alongside the Yarra River.

He said council may need to lobby hard on the issue. “[State Library board president] John Wylie and the board have indicated they’ll be with us every step of the way, to the minister, to make a claim that regardless of what was granted in 2007 under the CDP, this must be changed.”

Recent council modelling showed that at 236 metres, the tower currently proposed would start shadowing the forecourt at 1.56pm on June 22, breaching the planning scheme rules by a mere four minutes.

Council’s planning chairman Ken Ong said developers CES Victoria would have to chop 35 levels off the high-rise in order for it not to overshadow the forecourt before 2pm.

“Realistically, from an economic perspective, the developer couldn’t proceed if that was the case,” Cr Ong said.

He said he had also had engineers looking at changing the orientation of the building, but it had not solved the overshadowing issue.

Planning Minister Matthew Guy has final say on the project, as he does with all developments exceeding 25,000 square metres.

It is not yet clear how he will deal with the dilemma. In a statement yesterday he said “this permit application is being considered in light of the relevant planning provisions”.

Mr Wylie said the library’s forecourt was one of the great “iconic” public spaces in Melbourne that should be protected.

“Every time you see an image of the library, it’s usually of the forecourt there in the sunshine.”

Debate over the skyscraper’s impact on the State Library came in the same week Melbourne City Council said it had received another tower proposal that would overshadow one bank of the Yarra River.

Developer Mirvac wants to build a 38-storey office tower on Collins Street next door to the Intercontinental hotel. The 150-metre-high tower will retain heritage buildings fronting Collins Street.

The $50 million building, designed by architects Grimshaw, will overshadow the northern bank of the Yarra, but it will comply with the city’s planning scheme, which requires that no buildings overshadow the south bank of the Yarra at the height of winter between 11am and 2pm.