Federal New Democrats have begun a new campaign calling on B.C. voters to urge their MPs to stop the harmonized sales tax before it comes into effect on July 1.

On Saturday afternoon, New Democrat MPs Libby Davies and Don Davies were in Vancouver's Chinatown, where they joined supporters handing out a few postcards that people could send to their federal representatives in a bid to halt the HST.

Libby Davies told reporters the federal Conservatives and Liberals rammed through the "dreaded HST" bill last December with little debate.

"We know it's always been a Conservative plan to bring in the HST," she said.

Organizers of an anti-HST petition in B.C. have collected 600,000 signatures and signed up a minimum of 10 per cent of registered voters in all 85 provincial ridings.

The petition could see a law introduced in the B.C. legislature that proposes to dump the levy or a provincewide referendum on the tax in September 2011.

Federal NDP Leader Jack Layton sent a letter in April to Prime Minister Stephen Harper, urging him to put off implementation of the tax until the referendum process is complete.

However, Layton said nothing when Nova Scotia's NDP government boosted that province's HST two percentage points to 15 per cent in its April budget.

Davies said the grassroots initiative, led by former premier Bill Vander Zalm, has likely stunned MPs who supported the controversial tax, and now it's time they listened to voters.

"The governments that support the HST, they thought that well, nothing was going to happen. And I think they've probably been totally stunned by the incredible public reaction in every constituency in British Columbia," she said.

Premier Gordon Campbell has been criticized for misleading British Columbians by saying before the last election that the province would not introduce the HST, which combines the provincial sales tax and the federal GST to create a 12-per-cent value-added tax.

But federal Access to Information documents obtained by The Canadian Press showed that three days after winning last May's election, the province and Ottawa began working on a harmonized sales tax.

Campbell has called the tax one of the most important policy initiatives of the 21st century, arguing it will create thousands of new jobs and generate investment.

Critics say the HST is merely a $2-billion tax shift from big business to consumers.

Davies said families and small businesses will be hardest hit by the levy that has been opposed by the restaurant, tourism and housing industries because customers will have to pay higher costs.

B.C. will receive $1.6 billion from the federal government to implement the HST.

But Don Davies said there's no rush to bring in the tax before a possible referendum takes place, especially in light of the petition, which he called "one of the greatest expressions of public democracy in British Columbia history."

"The least that Mr. Campbell and Mr. Harper can do is respect that by not proceeding with the HST on July 1," he said.

"We think that the only democratic thing to do and the only smart public policy thing to do is to stop this tax now and let's wait and see what the people of British Columbia decide to do."

The HST is also set to be introduced in Ontario on July 1, but the grassroots opposition to the tax in that province wasn't anywhere near what it's been in B.C.

Along with Nova Scotia, Quebec, New Brunswick and Newfoundland and Labrador, already have forms of the harmonized tax.