A new ad campaign has Ontario Premier Dalton McGuinty telling consumers to swallow their medicine - the HST. (Canadian Press)

Premier Dalton McGuinty is telling Ontario consumers to swallow their medicine — the HST.

Ontario's Liberal party on Monday launched a TV ad featuring McGuinty dressed casually and sitting in a leafy backyard setting. He talks about the coming merged tax and his government's plan to grow the economy.

"Ontario is coming out of this global recession sooner and stronger than anyone expected," McGuinty says in the 60-second spot dubbed "Strong Medicine."

"Because of the hard work of Ontarians, we are again leading Canada in economic growth."

"But to create more jobs, top economists agree the single most important thing we can do is adopt the HST."

The TV spot was scheduled to run during newscasts across Ontario, starting Monday night at 6 p.m. The ad will also run online until July 1 — the day the harmonized sales tax takes effect in Ontario.

The HST will combine the existing eight per cent PST and the five per cent GST into a single 13 per cent sales tax.

Critics note tax harmonization will increase the cost of many items that were previously exempt from the provincial sales tax — from gasoline to Internet bills, haircuts and real estate fees.

McGuinty notes during the ad that "some things will cost more" but says there will be tax relief for some people to help ease the transition.

"I know the HST is strong medicine, but it's what we need to build a strong economy, so we can have the best schools, health care and quality of life," McGuinty says.

Ontario's move towards the HST has been bitterly opposed by the Progressive Conservatives and New Democrats, who say it will kick people when they're already down due to the recession.