A public service group’s plane chartered to fly an anti-Stephen Harper message around Ottawa was ordered to land by the RCMP Saturday, causing accusations police were limiting freedom of speech.

Larry Rousseau of the Public Service Alliance of Canada said the plane towing the message “Stephen Harper Nous Deteste” (Steven Harper Hates Us) had been flying in the Ottawa area for less than two hours when RCMP contacted the pilot and told them to land.

Rousseau said the pilot was then “interrogated” once he was on the ground, accusing them of getting involved for political reasons.

"Was it because you didn't want the PM to see the banner?" he said. "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 PM anymore? That's a real concern for us."

The RCMP said they told the plane to land as part of their mandate to protect the prime minister, as it could have posed a security risk.

The PSAC said its flight plan was pre-approved and didn't violate restricted airspace.

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

It had flown without incident in other cities and has moved on from the capital region, but the union said it's planning to fly it around Ottawa sometime around Sept. 17 when Parliament resumes..

With a report from CTV Ottawa’s Ellen Mauro