The Conservatives have launched a fresh series of Internet ads in which they denounce the environmental policies of Opposition Leader Thomas Mulcair and his New Democrats as "risky" and "dangerous."

The new ads can be viewed in English and French on the Conservative Party website and YouTube channel.

When Mr. Mulcair won the NDP leadership in March, it was assumed the Conservatives would waste little time creating messages in an attempt to discredit him.

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They had destroyed the electoral hopes of two previous Liberal opposition leaders using similar tactics. Stéphane Dion was declared to be "not a leader" and Michael Ignatieff was portrayed as "just visiting."

The new ads targeting Mr. Mulcair – which come as repeated polls suggest the New Democrats have a small lead over the Conservatives – are less mocking and more ominous than those that that took aim at his predecessors on the Official Opposition bench.

In English, they warn the NDP has some risky economic theories.

"They think strong growth in some industries is a disease that actually needs to be slowed down with more taxes and higher prices," a male voice says in a foreboding tone over black-and-white footage of Mr. Mulcair talking to a camera. The line is a reference to Mr. Mulcair's assertion that the economy is suffering from "Dutch disease," meaning that allowing oil sands development without demanding a greater price for their toll on the environment is driving up the dollar and hurting a wide range of other industries, including manufacturing, fishing and forestry.

The French ad, however, does not mention Dutch disease.

It asks viewers if they really know Mr. Mulcair, and says he would impose a carbon tax on things like gas and electricity.

The French ad praises Prime Minister Stephen Harper for his record on job creation, while the English version is strictly an attack on the NDP Leader and his party.

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"Mulcair's NDP even oppose trade agreements that will increase exports," the English-language ad says.

"Risky theories. Dangerous economic experiments. We can't afford Mulcair's NDP."

The Conservatives refused to say Monday whether they have bought television spots to air the ads or will allow them to stand as an Internet product.

The NDP said when it became the Official Opposition last year that any attack ads from the Conservatives would be met in kind, but is was unclear what, if any, response the party would have in this case.