The NDP says it will no longer stand by and watch as the Conservatives "shut down" debate on its budget bill, as a coalition of environmental groups launches a national ad campaign to protest proposed changes to environmental laws in the bill.

In an interview airing on CBC Radio's The House on Saturday, NDP Leader Thomas Mulcair said the party is reaching "a breaking point" with such behaviour from the government, and is contemplating "legal" as well as "parliamentary" options.

"This is the 18th time that the Conservatives have invoked closure; it's unprecedented," Mulcair told host Evan Solomon.

Conservative MPs voted last week to limit debate on the 431-page budget implementation bill, leaving all MPs with less than a week to debate it at second reading stage before it heads to committee.

Conservative MPs justified the vote by saying there will be "more debate" on this bill than the Liberals ever had on any of their budget bills.

"We can't have a Parliament that's not open to the public that elected it," said Mulcair, adding that "as the Official Opposition, we're going to have to take some tough decisions in the coming weeks and months."

Environmental groups launch campaign

Also beginning on Monday, a coalition of environmental groups is launching a national ad campaign to protest what they see as the federal government's "war" against the environment.

Nearly a dozen environmental groups, including Greenpeace, the World Wildlife Fund, and the David Suzuki Foundation will take out newspaper ads to draw attention to proposed changes to environmental law contained in the government's latest budget implementation bill.

The Black Out, Speak Out campaign calls on Canadians to raise their voices against proposed changes to environmental law — changes environmental groups say will "weaken environmental rules and silence the voices of those who seek to defend them."

In an interview with CBC News on Sunday, executive director for Sierra Club Canada John Bennett said: "What we want is the environmental law changes out of the budget. They have no business being in the budget."

"If the government wants to change environmental law they should put forth an environmental bill, and they should have consultation hearings across the country. But sticking it in the budget is a coward's way of doing it," said Bennett.

While Environment Minister Peter Kent was not immediately available for an interview, Kent has said that the changes are simply about updating decade-old laws.

Speaking in the House of Commons last Thursday, Kent defended the budget implementation bill saying "the responsible resource development is an intelligent approach to environmental protection that goes hand in hand with the resource development that creates jobs and wealth for Canadians."

Kent under fire for comments

On Friday, Canadian charities demanded that Kent retract accusations that some charitable groups are "laundering" foreign funds in Canada.

Imagine Canada — an umbrella organization representing the charitable sector — wrote an open letter to the minister expressing "serious concern" over his repeated use of the word.

Mulcair told Solomon on Saturday he agreed that "Peter Kent should not only retract; he should apologize."

The coalition of environmental groups will be urging other organizations to join them in an online protest next month.

The environment groups plan to black out their websites on June 4, 2012, to protest what they see as the government's "effort to silence" environmental voices.

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