Environmentalists are expressing concern about the NDP's deal with the Conservatives to revamp the much-maligned Clean Air Act.

Prime Minister Stephen Harper agreed to NDP Leader Jack Layton's proposal to send the act to a Commons committee for study before second reading -- a highly unusual move.

Layton said the deal was a victory: "This breaks the parliamentary logjam.

"What has been achieved over the last 48 hours means that this minority parliament will move forward on vital climate change legislation. This is a victory for all Canadians."

However, new Green Party Leader Elizabeth May said bringing the Clean Air Act into committee would give the legislation some legitimacy it doesn't deserve.

"Saying that there's any hope of breathing life into this really appallingly bad legislation is confusing, and does appear to have given Harper new legs to say this bill is acceptable.''

Activists in the environmental community thought there was a unified opposition strategy to bury the bill.

The also fear Layton's move distracts from a private member's bill put forward by Liberal MP Pablo Rodgriguez that would have required the government to respect the emissions-cutting protocols of the Kyoto Protocol.

"Some people are apprehensive,'' Dale Marshall of the David Suzuki Foundation told The Canadian Press on Wednesday.

"The opposition was united around Kyoto and the Rodriguez bill and the government was clear it was only interested in delay. It was very clear where things were going. Now there's a lot more balls in the air and it makes people antsy.''

On Tuesday, before meeting with Harper late in the day, Layton gave the prime minister a deadline to rewrite the contentious Clean Air Act.

The NDP leader threatened to file a non-confidence motion against the government on Thursday if Harper didn't take action -- although he would require the support of the Bloc Quebecois and the Liberals to defeat the government.

The agreement appears to forestall an immediate confrontation in the Commons.

He also tabled a private member's bill on Tuesday that called for action on climate change but didn't even mention the Kyoto Accord.

May thought the NDP were trying to differentiate themselves from the Liberals, and suggested Layton was trying to steal some of the thunder from Rodriguez's bill.

The government has taken serious criticism over the Act since its release. All opposition parties oppose it, primarily because it doesn't set greenhouse gas reduction targets before 2050.

Robert Fife, CTV's Ottawa bureau chief, said the new agreement between Harper and Layton will provide the opportunity to resolve many of the key disagreements.

Both sides still have to determine what committee will review the bill, according to a Harper spokesperson.

Speaking after his caucus's meeting, Layton expressed optimism the Clean Air Act could be transformed into something that would respect the Kyoto Protocol and be good for the environment.

Fife said the move comes as "a bit of a slap in the face" for Environment Minister Rona Ambrose," who originally tabled the Act.

Critics say the legislation fell short of Ambrose's promise of new environmental laws that would be tougher than anything previously seen.

"She oversold something that wasn't going to stand up," Fife said.

With files from CTV's Robert Fife and The Canadian Press