MP Bruce Hyer, a former New Democrat who announced today that he has joined the Green Party, had some harsh words for Tom Mulcair on Friday, saying the NDP leader's stronghold over his caucus is shameful.

In an interview airing Friday on CBC News Network's Power & Politics, Hyer and Green Party Leader Elizabeth May rejected the NDP's assertion that Hyer ought to resign his seat and run in a byelection.

Hyer defended his move to the Greens telling guest host Rosemary Barton, "I joined the Jack Layton party. It's not the Jack Layton party anymore."

TODAY ON POWER & POLITICS: You can watch the full interview with Green MPs Bruce Hyer and Elizabeth May on CBC News Network's Power & Politics today at 5 p.m. ET. 

He added: "Mulcair is following the model that has been set by some leaders before him of control and muzzling, and lack of democracy to put it bluntly."

Hyer said he did not support Mulcair when he ran for the leadership of the federal New Democrats following Layton's death from cancer.

"If Nathan Cullen, or Paul Dewar, or Niki Ashton, or several others had been made leader I'd still be there," Hyer said.

During the NDP leadership race, Hyer backed Cullen as his first choice and Mulcair as his second.

NDP wants Hyer to resign seat

During the interview, May defended Hyer and pointed out his decision to join the Greens did not come overnight.

"He's been sitting as an Independent for nearly two years, in order to best represent the people of Thunder Bay-Superior North and that's where his alliance and allegiance lies."

NDP ethics critic Charlie Angus called on Hyer to immediately resign his seat and run again in a byelection, in a written statement issued after Hyer's announcement Friday morning.

"Hyer has broken faith with the voters. We are calling on him to do the right thing, the honourable thing, and immediately resign his seat and give the voters of Thunder Bay-Superior North a real choice in a byelection," Angus said in a written statement.

Angus accused Hyer of leaving the NDP caucus because he was not given a role in the party's shadow cabinet and said he is now betraying his constituents by joining a party they did not vote for in the last election.

During his interview on Power & Politics, Hyer responded to the criticism from Angus saying, "the NDP got 29 per cent of the vote across Canada last time, I got 50 per cent."

Party discipline

Hyer was in Thunder Bay, Ont., on Friday morning where he announced his decision to join the Green Party, almost two years after leaving the NDP caucus.​

A longtime advocate of democratic reform, Hyer said he will now have the resources of the "only truly democratic party" in the House of Commons — a not-so-subtle jab at the federal New Democrats.​

Hyer left the NDP caucus on April 23, 2012, after party discipline required New Democrat MPs to support the long-gun registry, something the MP for Thunder Bay-Superior North said he could not do.

The NDP had previously disciplined Ontario MP John Rafferty for siding with the Conservatives during a vote to dismantle to gun registry.

Hyer had high praise for May whom he said was "the only leader that seeks consistently day after day co-operation and compromise with other parties out of respect for all of the MPs in the House."

He said May has promised him his votes will not be whipped, unlike the Conservatives, NDP and Liberals who "still require lockstep discipline in the House with little room for meaningful public debate."

John Percy, leader of the Green Party in Nova Scotia, welcomed the former NDP MP, saying in a post on Twitter, "Welcome to Bruce Hyer, a man who understands 21st century politics."

Last week, Conservative MP Michael Chong tabled the proposed reform act, a private member's bill that would restore power to MPs in the House of Commons.