A plane towing an anti-Stephen Harper message around Ottawa was ordered to land by the RCMP, leaving the group behind the message questioning their right to freedom of speech.

The Public Service Alliance of Canada (PSAC) chartered a small plane to fly a banner that read “Stephen Harper Nous Deteste” (Steven Harper Hates Us) on Saturday.

The banner is part of a Quebec-wide campaign by PSAC to protest federal public service cuts.

According to the RCMP, the plane was ordered to land because it could have posed a security risk to the prime minister.

In an email to The Canadian Press, an RCMP spokeswoman said the plane appeared to be flying in restricted airspace over Parliament Hill.

However, the union said the flight plan was approved in advance and the plane didn’t violate restricted air space.

Union executive vice president Larry Rousseau said the plane was flying for less than two hours when the RCMP radioed the pilot and ordered him to land.

Rousseau said once he landed, the pilot was interrogated.

"Was it because you didn't want the prime minister to see the banner?" Rousseau asked. "Who knows, but we're very concerned that this is not about hate speech, this is about freedom of speech.”

“Are we really not allowed to criticize the prime minister anymore?” Rousseau asked. “That's a real concern for us."

The PSAC had flown the banner over Quebec cities in recent weeks without any problems.

The union said it’s contemplating a second attempt at a flight through the country’s capital.

With a report from CTV Ottawa’s Ellen Mauro