Adding insult to injury, the Liberal MP says it was his idea to display the iconic robotic space arm at a public museum, rather than have it moulder in obscurity at the Canadian Space Agency's headquarters near Montreal.
Garneau is Canada's first astronaut and a former head of the space agency.
He operated the Canadarm on two of his three space missions.
Yet that wasn't enough to earn him an invitation to Thursday's exhibit opening at the Canada Aviation and Space Museum.
He blames Conservative partisanship for the snub, although the government insists it had nothing to do with compiling the invitation list.
"I think it's impolite, it's disgusting," Garneau said of the snub, accusing the government of being "hyper-partisan all the time."
"I'm not surprised by this government but I do seriously feel insulted," he added.
"I operated (the Canadarm) on two of my missions. I've been involved with the space program. It's because of my efforts that the arm is in the museum here in Ottawa rather than being at the Canadian Space Agency where nobody would have seen it."
The Canadian-invented robotic arm, featured on the new $5 bill, was a key part of NASA's space shuttle program for almost 30 years. NASA retired the arm in 2011.
Initially, the Canadarm was to have been sent to the Canadian Space Agency but Garneau said he wrote Industry Minister Christian Paradis urging him to ensure it was displayed publicly at a national museum.
During question period Thursday in the House of Commons, a Conservative MP lobbed a planted question about how the government intends to celebrate "this amazing Canadian invention."
As Canadian Heritage Minister James Moore rose to praise the new museum exhibit, Liberal MPs chanted Garneau's name.
"Members opposite can obsess about their caucus and maybe we will obsess about Canadian history," Moore said.
"Today we had the unveiling of the Canadarm at the museum and we look forward to thousands of Canadians coming through that museum, seeing the Canadarm and seeing its remarkable contribution to Canadian history."
Moore's spokeswoman later said invitations were issued by the space agency and the museum, which organized the opening.
"The minister's office was not consulted on invites whatsoever," Jessica Fletcher said.
A space agency spokeswoman said invitations were solely the museum's responsibility.
Another Liberal MP, Mauril Belanger was at the opening. The museum is located in his Ottawa riding and Belanger said the museum director informed him of the event. He was surprised when he discovered Garneau had not been invited.
"I believe he should have been there. I mean, come on, how many MPs have actually used the Canadarm in space?"