The planners behind the controversial Château Laurier hotel expansion have threatened legal action if Ottawa city council reverses its decision to allow the addition at its meeting next week.

In a letter dated Wednesday, the planners working for Larco Investments, the Vancouver-based owners of the historic hotel — urged members of council to reject Coun. Mathieu Fleury's motion to revoke council's June 2018 approval. The debate and vote will take place on July 10, the last council meeting before the summer break.

"Such a revocation is probably not legally permitted and would no doubt result in costly litigation at taxpayer expense with the likely result that the approval would be upheld by the courts," the emailed letter said.

Momentum's chief planner, Dennis Jacobs, far right, co-wrote a letter to councillors warning them against revoking the approval for the unpopular Château Laurier addition. (Joanne Chianello/CBC)

The letter is signed by two executives of Momentum Planning and Communication, principal planner Dennis Jacobs, who was once the city of Ottawa's planning director, and president Suzanne Valiquet, also a member of the Ottawa Police Services Board.

That the hotel owners would legally challenge a council decision to try to block the expansion isn't a surprise, but the email makes it clear that "litigation" is Larco's next move if council revokes the approval for the addition.

Council can change mind, lawyer says

Despite what Larco's planners say, the city's own legal department says council has every legal right to revoke the heritage permit it issued last year. The permit allows Larco to make changes to the heritage building.

Ottawa's planning lawyer, Tim Marc, told the planning committee last month that council can revoke the heritage permit up until the time that a building permit is issued. In short, council is within its legal right to change its mind, until it no longer can.

Of course, any council decision to pull the heritage permit would come with consequences, the most obvious being that the Château Laurier's owners would legally challenge the move.

Marc told councillors taxpayers would be on the hook for about $200,000 in fees to defend council's decision in the face of potential action from Larco.

Is fighting Château addition worth $200K?

Whether $200,000 constitutes "costly litigation" in the eyes of many residents is unclear. After all, the Château Laurier expansion has been very unpopular — all five versions of it.

Councillors have said their inboxes are full of emails from frustrated residents who detest the proposed addition, which has also been excoriated on social media. As of Thursday afternoon, more than 5,600 had signed a petition to block it.

Local architect Barry Padolsky circulated his own rendition of the Château Laurier addition, showing it virtually obliterating the view of the historic hotel from Major's Hill Park. (Provided by Barry Padolsky)

The letter from Momentum also addresses a version of the addition from the viewpoint of Major's Hill Park that has been circulated by local architect Barry Padolsky, a member of the city's built heritage subcommittee.

Padolsky wrote to Prime Minister Justin Trudeau on Canada Day to intervene in the Château Laurier addition. In his letter, which he circulated to media, Padolsky included his own drawings showing the addition all but obliterating the view of the heritage building from the park.

The planners for the Château Laurier hotel owners prefer this view of the addition from Major's Hill Park. (Provided by Momentum Planning and Communications.)

Momentum argues Padolsky's rendition is "architecturally correct," but complained that it was taken "from a much closer vantage point … to exaggerate the mass and height of the addition."