VANCOUVER -- Elizabeth May says she supports civil servants' right to free speech -- and free song.

The Green Party leader welcomed former federal scientist Tony Turner to retirement by bringing him on stage at a Vancouver campaign rally to sing his viral folk song "Harperman."

The scientist announced his resignation this week, after he was placed on leave this summer for allegedly breaching the federal government's values and ethics code for public servants by recording and posting the song on YouTube.

May clapped and sang along in the background as Turner performed the tune, which criticizes the prime minister's policies and concludes, "Harperman, it's time for you to go."

The former Environment Canada employee told a crowd of more than 100 Green supporters that he resigned because he didn't want to be sidelined any longer. He said he wanted to speak before the election about things he cared about deeply.

"We have this leadership that is appealing to our base instincts of fear, hatred, selfishness, greed. That's what our government is doing to appeal to voters. And I think we're better than that. I know we're better than that," he said.

"We want a leader who inspires us, who talks about co-operation, about fairness, about justice."

May told the cheering audience that she wants to restore science to the core of decision-making in the government of Canada.

"We say yes to a future built on common sense, human decency, and please, evidence. We say yes to science. We say we have to come back and employ the scientists that Stephen Harper fired. We have to take off the gags and the muzzles."

Critics have accused Harper of restricting federal scientists from publicly talking about their own research as well as firing scores of researchers in the past four years.

At the eco-friendly rally in a park -- where the stage was partly powered by people riding stationary bikes -- climate change was a major focus of May's speech.

She vowed to block all the major pipeline proposals, including Kinder Morgan's Trans Mountain pipeline expansion, which would increase the number of tankers in Metro Vancouver's Burrard Inlet seven-fold.