Prime Minister Stephen Harper has defended Tory senators who voted down a climate change bill ahead of an upcoming United Nations meeting on the issue in Mexico.

Harper, in responding to a query from NDP Leader Jack Layton in question period Wednesday in Ottawa, said Conservatives have been consistent and clear in their opposition to Bill C-311, which the prime minister called "a completely irresponsible bill."

"It sets irresponsible targets, doesn't lay out any measure of achieving them other than ... by shutting down sections of the Canadian economy and throwing hundreds of thousands and possibly millions of people out of work," Harper said. "Of course, we will never support such legislation."

Layton argued Harper had no right to use his "unelected senator friends" to kill the bill, which he called the will of the House.

"He's lost his moral centre," Layton said. "He's fundamentally undemocratic, Mr. Speaker. Let's be clear about it, that's the truth. He broke his promise to bring our troops home, which this House asked for. He broke his promise to have votes on the use of our troops in foreign wars.

"He broke his promise never to appoint unelected senators, and now, he's using them to subvert the will of this House. It's never happened before. It should not be permitted, and where is his democratic impulse?" said Layton.

'Another ambush move'

Earlier in the day, another NDP MP called it "another ambush move" by the Harper government.

"I'm still reeling from the shock, but after no debate, no consideration at all, all of a sudden in another ambush move by Stephen Harper, the Senate voted yesterday to kill the climate change [bill] without debate," said Bruce Hyer, MP for Thunder Bay-Superior North.

Bill C-311, which was voted down 43-32 late Tuesday, would have called on the government to establish five-year plans to meet greenhouse gas emission targets by 2050, according to Liberal Senator Grant Mitchell, the author of the bill in the Senate.

The bill was passed in May by the House and went to the Senate for final approval.

There is debate about who actually initiated the Senate vote, with each side saying the other was responsible.

"Killing Bill C-311 shows a fundamental lack of respect for the many Canadians who care deeply about climate change. They had a right to have this bill debated properly," Mitchell said in a news release.

Mitchell later told reporters in Ottawa that it was an unprecedented move to defeat a bill that had been passed by Parliament.

"They would defeat a bill in the Senate that was passed in the House of Commons by a majority of elected members of Parliament," he said. "Not only did they defeat it but defeated [it] before it even got to a committee stage, where it could have more airing."

It's 'one of the most anti-democratic acts' seen in Parliament, says NDP Leader Jack Layton, shown in Ottawa on Monday. (Sean Kilpatrick/Canadian Press)

The bill — the Climate Change Accountability Act — has spent the last year or so bouncing between the full House of Commons and its environment committee.

The legislation called for greenhouse gases to be cut 25 per cent below 1990 levels by 2020. That level is more stringent than the Harper government's goal of a 17 per cent emissions cut from 2005 levels by 2020, which is in line with the U.S. administration's targets.

'We aren't giving up'

"We worked on this bill for five years. The vast majority of our elected representatives voted for it. It was killed in the night by trickery," said John Bennett, executive director of Sierra Club Canada.

"We aren't giving up. We will continue to work with mothers and fathers who want a brighter future for their children. We will find the solutions," said Bennett.

The Sierra Club said the bill was developed with the participation of scientists and environmentalists and "was passed by a significant majority of members of Parliament and was supported by a petition signed by more than 150,000 Canadians."

The government can prevent any bill from coming on to the Senate floor for debate, said the NDP's Hyer, and "they've done that for 193 days, and the first opportunity they got after not enough Liberals were around, they moved quickly to kill the bill."

"A number of our Conservative senators — who darn it, won't go on the record — have told me that the [Prime Minister's Office] has ordered them not to speak about the climate change bill, not to allow it to come up for a vote and to kill it when they could," Hyer said.

Canada has one of the worst records in the world on climate change and the Tories are using the Senate "as a strictly political tool," he said. "Everyone is in shock about this."

UN delegates will meet in Cancun later in November in an effort to broker a climate-change deal.

With files from The Canadian Press