Cohlmeyer Architecture designed Regina's square plaza and is now asking for an extra $600,000. (CBC)

The City of Regina is facing a lawsuit from an architectural firm for what it claims is an unpaid bill.

Cohlmeyer Architecture designed Regina's square plaza project and is now asking for $600,000.

The firm said as the project's costs kept increasing so did the company's fees.

But the firm said the City refuses to pay the extra money.

Colin Craig with the Canadian Taxpayers Federation said this is the latest controversy at City Hall on money mismanagement.

"If you look at this recent lawsuit one has to ask, 'well who is going to be held accountable at the city for those mistakes,'" he said.

The city square plaza project cost $12.6 million, which is almost double the original projected budget.

Independent audit sought

On Tuesday, a candidate for a seat on Regina's city council called for an independent audit on the costs associated with the plaza project.

“I’m not surprised by the lawsuit,” Eric Anderson said in a news release. “To me this is the tip of what is a very large iceberg. This project has been clearly been mismanaged from its inception."

Anderson added that, in his view, information regarding the financial details of the project have been "severely lacking".

“This current council wants to spend hundreds of millions of taxpayer dollars on a football stadium, yet they can’t even manage the costs of a key downtown street,” he added. "Is Regina's square plaza project a sign of things to come for future large scale city projects?"