Simpson Oil, which holds about a 19.7% stake in Parkland, had agreed in December to waive its rights to nominate new directors until March 31. Last week, Parkland announced plans to hold its annual general meeting (AGM) on March 28.

"For the past 10 years, Parkland has held its AGM in the month of May. Simpson Oil waived its rights under the Nomination Agreement on 31 December 2023 in the expectation that it would be able to exercise its shareholder rights free from any restrictions at Parkland's 2024 AGM," Simpson Oil said in a statement.

The rift between Calgary-based Parkland and its biggest shareholder came to a head in December when Simpson's nominees Marc Halley and Michael Christiansen exited Parkland's board abruptly and Simpson signed an agreement with Parkland the same day, which prohibits the oil company from making any public statements against Parkland.

Parkland did not respond to a Reuters request for comment.

Parkland is already facing pressure from activist investor Engine Capital which warned the Canadian company in January not to pursue "wasteful litigation with its shareholders" and urged the company to appoint independent board directors.

Engine had said at the time that it was concerned about the departures of Halley and Christiansen after being directors for eight months. The U.S.-based activist Engine had earlier urged Parkland to divest assets.

Simpson Oil said following the 2024 annual general meeting and the termination of the nomination agreement, it "will evaluate and consider its ability to fully exercise and protect its shareholder rights."

Parkland is one of Canada's largest fuel retailer with a market value of about $5.53 billion.

(Reporting by Utkarsh Shetti in Bengaluru;Editing by Dhanya Ann Thoppil)