THE key role played by the Labour leader of Glasgow City Council in the abandoned £15 million overhaul of George Square has been laid bare in a scathing leaked report from the professional body which ran the design contest.

The Royal Incorporation of Architects in Scotland (RIAS) says Gordon Matheson was at the heart of a "debacle" which brought the city into "significant disrepute", and cost taxpayers £100,000 and architectural practices a further £200,000.

In the first authoritative insider account of the shambles, which ended with Matheson scrapping the revamp of the square just minutes after a winning design was chosen, RIAS reveals the leader:

l personally drove the redesign process throughout

l insisted that he was chair of the judging panel, usurping the role of the official chair

l deeply resented the winning design, which he considered "disrespectful" to Glasgow

l rejected RIAS advice on good practice

l temporarily "abandoned" the judging process, leading to it being lampooned in the media

l and directly contributed to a "very significant waste of public and private resources"

The findings went before the ruling council of RIAS last week, and will now be shared with the public spending watchdog Audit Scotland, which is already looking at George Square as part of its 2012-13 audit of the council's management.

The SNP and Tories on the council last night urged Matheson to apologise over the affair.

The RIAS report adds to the pressure on Matheson ahead of the council's Labour group AGM in May, when he could face a leadership challenge.

It says that at the first judging session, on January 14, Matheson indicated "that in his view scheme number six [by architect Burns + Nice] was by far the best submission".

On January 21, the judges signed off a design by John McAslan as the winner, while Matheson's favourite was ranked fourth.

It adds: "At this point, Councillor Matheson indicated that his administration would not be proceeding further with any of the designs." Matheson then said the square would undergo a modest facelift instead, according to the report.

In a devastating conclusion, the report adds: "From his initial comments at the first judges' meeting onwards, it appears that, for whatever reason, Councillor Matheson had selected his own winner at the outset and reasoning by a very experienced group of judges did not persuade him otherwise."

Graeme Hendry, leader of the SNP opposition on the council, said: "Councillor Matheson's repeated attempts to rewrite history and cover up his failings in the George Square fiasco are shameless. It seems clear he had no intention of running a serious competition. An apology is long overdue."

Tory councillor David Meikle added: "Surely the Labour group will wonder in light of this if Councillor Matheson is the right man to be leader?"

A RIAS spokesperson said: "We do not comment on leaked documents."

A Glasgow City Council spokesman refused to comment on the criticisms of Matheson.

However, he insisted the judging process had been well run, and that the winning architect agreed.

"We agree with Mr McAslan that the judging process was carried out appropriately and we share his disappointment that it was not possible to proceed with the winning design."