John McAslan attacked officials at Glasgow City Council as "not that bright" after they pulled the plug on the £15 million plans, despite spending in excess of £100,000 on the initiative.
He said the debacle had given the local authority an unwelcome reputation among the world's architecture and design community.
Insisting he would continue to press council leader Gordon Matheson to reinstate his design, Glasgow-born Mr McAslan said he believed his winning blueprint had been pulled, in part, because it was not the design many in the authority had wanted.
The London-based architect, whose design included input from Turner Prize winner Richard Wright, said his plans could have been delivered for about £3m less than the proposed budget without tampering with the square's history by retaining all the statues.
The Herald also understands revelations last week about Mr Matheson committing a sex act in public weakened his position within the Labour administration amid concern among party colleagues over how the George Square plans were being received in their local wards.
It is understood the council leader, who has been the individual driving force for the plans including the desire for a water feature, gave into the pressure.
Sources have indicated that, while critically wounded by the fiasco and sex revelations, there is no appetite to mount a challenge against Mr Matheson or support for those who may harbour ambitions for the top job.
On Monday, Glasgow said it had selected a winner from the shortlist of six designs commissioned in an international competition, but added they would not be implemented. It will proceed with much more modest proposals, U-turning on plans to remove the centuries' old statues, retaining the grass areas and replacing the red tarmac.
Mr McAslan said: "Gordon Matheson has chosen to ignore the process, the views of the jury and his officers, for whatever political reasons and is now off to work up his own proposals.
"He's wasted time and resources. It's not the way to behave or to run a serious process. It seems to me he didn't like the result of the competition and terminated it.
"You didn't get the sense there was ever any enthusiasm or ambition to fulfil the pledges the council had made over George Square. This should have been the beginning of a process of engagement. There was posturing, some excitement and then they pulled the plug.
"There's incompetent governance at the heart of the city council and Gordon Matheson has allowed this to happen.
"He is the chap ultimately responsible. We will not be bullied by Gordon Matheson over this."
He added: "The next time Glasgow has any design competition, potential bidders will first of all ask themselves how this has happened, then will the council change its mind depending on what is politically beneficial for it. They'll then ask why they should go through all that.
"The people who pulled this are not that bright. They don't realise we're tenacious. We will continue to pursue this positively and while there may be legal avenues that's not a route we'll be going down."
The council's SNP chief, Graeme Hendry, said: "Councillor Matheson is now looking at a scaled-down piece of work so needs to explain why he is still planning to spend £15m on it. Surely a scaled-down project should free up the council's £5m contribution for other vital projects in the city? That he is still talking about spending £15m suggests this is desperate, reactionary policy being made on the hoof."
A council spokesman: "Under the procurement process for the design contest, the jury had to conclude its deliberations and choose a winner, and that part of the process was completed on Monday.
"The next stage of the process was for the council to decide to award the contract to the winning company."