It’s another bombshell surrounding the construction of the Downtown Winnipeg Police Service Headquarters.

Mayor Brian Bowman said the city wants to sue over the scandal-plagued building, but it can't because of a roadblock put in place under the former Sam Katz administration.

"I can't explain it, makes no sense to me," said Bowman.

Bowman said the contract signed with the firms responsible for construction, Caspian and engineering design consultants AAR, prevents the city from filing a lawsuit over deficiencies with the building.

"It demonstrates the city's interests and city taxpayers interests weren't paramount," said Bowman.

And that's not all. Bowman and Winnipeg CAO Doug McNeil said a law firm, outside city hall, was used to draw up the contract, not city lawyers.

"Very few public servants were permitted to be involved in this project," said McNeil.

The mayor says the city is left with no choice but to go to binding arbitration to recoup money.

"The city, under the previous administration, you know, tied its hands to arbitration," said Bowman.

The police service has dealt with deficiencies including water leaks, heating and electrical issues. McNeil would not identify which ones will be named in the arbitration, or the grand total.

"It's a significant amount of money,” said McNeil, referring to what they city would like to recoup.

The project was roughly $80 million over budget and is the subject of a criminal probe by RCMP. With the revelation of the contract, Mayor Bowman is again calling on the province to hold a public inquiry.

The Pallister government would not rule one out but won't take action until the Mounties have done their job.