Former premier Bill Vander Zalm's campaign against B.C. adopting the Harmonized Sales Tax got a federal boost Thursday when NDP Leader Jack Layton joined the fight.

Vander Zalm was in Langley Thursday night rallying with hundreds of taxpayers who turned up to sign his group's petition against the tax.

HST opponents have two and a half months to collect signatures from at least 10 per cent of registered voters in each of B.C.'s 85 ridings if they are to have any hope of beating the tax.

Under B.C.'s recall and initiative law, if they succeed by July 5 they can force a referendum. But even if it passes, the result is non binding on the government – and the tax is due to take effect on July 1.

That's why Layton is calling on the Harper government to put off implementing the tax in B.C. until a potential referendum can be held.

Layton sent a letter Thursday to Prime Minister Stephen Harper urging him to suspend imposition of the tax -- which blends the GST with the provincial sales tax but applies it to more goods and services -- until the referendum process is complete.

It's easier to put the tax in limbo now rather than try to rescind it if the referendum succeeds, the letter says.

"We're here to support the people of British Columbia, who are rising up in unprecedented numbers using the democratic tools that are available to say No to a tax they were told would never be imposed on them by the Campbell government and the Stephen Harper Conservatives," Layton told reporters inside a crowded family restaurant in East Vancouver.

The provincial Liberals negotiated the HST deal last year weeks after winning re-election in a campaign where they insisted they weren't interested in the tax.

The tax deal with Ottawa, which included $1.6 billion in federal dollars to help implement it, has cut into Liberal support and triggered a grassroots campaign against the HST.

"A lot of people who haven't been involved in politics are becoming involved in this whole signatures process across the province," said Layton.

Vancouver-Kingsway MP Don Davies said there's no hurry to implement the HST while the referendum process takes its course.

"They can hold off several months and they can do so when it's the democratic expressions of the people of British Columbia that are at stake," he said.

The furor over the HST in British Columbia contrasts with a more muted opposition in Ontario, which has no similar referendum law, Layton noted. That may change once the tax starts to bite after July 1, he said.

"I must say, as is often the case, the people of British Columbia are kind of rising up with a more intense enthusiasm as we often see in the politics of British Columbia," said Layton, who represents a Toronto riding.

"The sleeping giant of popular opinion in Ontario's a little slower perhaps to express itself in such a significant way, but it's coming."

A list of locations available to sign the petition can be found at the Fight HST website.

More information on the tax is available at the B.C. government's HST website.

With files from The Canadian Press