Progressive Conservative Leader Brian Pallister says the number of people who have used Standupmanitoba.com is proof there is public opposition to the tax increase.
The NDP government raised the sales tax to eight per cent from seven per cent on July 1, and dodged a referendum that is required under the balanced budget law.
The government has said the tax hike is needed to pay for infrastructure projects and preserve front-line services.
But Pallister says the government should cut spending instead.
The bill to formalize the tax hike has been held up by Tory stalling tactics, and is expected to come to a vote in December.