ICBC is taking its union to B.C. Supreme Court over an alleged dirty tricks campaign in the midst of a labour dispute.

In a claim filed Monday morning, ICBC accuses employees of misusing company emails.

"The union has asked its members to alter their official ICBC communications signature on their email accounts and we are taking the position that this is an inappropriate use of ICBC’s trademark, of our property and of our business systems," said ICBC spokesperson Mark Jan Vrem.

"We’ve asked them to stop. They have not done so, so we’ve gone to court to take action."

Unionized employees gave 72-hour strike notice last month but must maintain essential service levels.

According to ICBC, about 1,000 employees changed their email signatures from "Building trust. Driving confidence," to "The B.C. government is taking $1.2 billion out of ICBC’s revenue. We work. You drive. We both deserve better."

ICBC alleges the new sign-off directs email recipients to the union’s website.

"We’re in the middle of a labour dispute right now and frankly, these types of actions on the part of the union are not unusual," Jan Vrem said.

Jan Vrem said it's not clear how many emails were sent out with the altered signature. According to the claim, about 10,800 emails with the altered signature were sent out on July 18 alone.

"We’ll probably see more of them, but we take strong exception to the inappropriate use of our trademark in this manner."

ICBC is seeking an injunction against the altered emails, as well as the use of its trademark images and phrases. The insurer is also seeking damages for any business lost.

The Union of Canadian Office and Professional Employees said Monday that members have a right to protest in this way.

"I don't see it as any different from our members wearing a button in the workplace or handing a leaflet out to clients as they come into the workplace," said spokeswoman Lori Mayhew.

"It's one way that we can deliver the message without disrupting service to the drivers."

With files from the CBC's Jason Proctor