Liberal Dwight Duncan, Ontario's finance minister in the past legislative session, is guaranteeing his party will not raise taxes or implement new fees if elected in October.

Duncan made the guarantee in an interview with CBC Radio's Matt Galloway on Metro Morning on Thursday.

"If the Liberals are re-elected, will that government raise taxes or introduce new fees that feel like taxes?" Galloway asked Duncan.

"No," Duncan replied. 

"That's a pretty straightforward answer. And that's a guarantee?" Galloway then asked.  

"Absolutely," Duncan said. "We've actually been cutting taxes for the last three years. Our tax plan for jobs and growth — we've cut personal taxes, we have cut business taxes and we've created the most general sales tax credit in Canada."

The Liberals made similar guarantees not to increase the tax burden on Ontarians in the run-up to the 2003 and 2007 elections.

But after they were elected in 2003, the Liberals introduced the so-called Ontario Health Premium. More recently, the government introduced the Harmonized Sales Tax, under which a number of items not previously taxed to the old provincial sales tax were subject to new levies.

Duncan insisted in the interview that unlike the Conservatives and New Democrats, the Liberal platform is fully costed and realistic. The Tory platform, he added, would result in cuts to health care and education as well as higher taxes.

NDP Leader Andrea Horwath, while campaigning Thursday in northern Ontario, expressed disbelief when told of Duncan's comments on Metro Morning.

"This is a promise that's been made many times before," said Horwath. "Did he cross his fingers behind his back? We all know they made this pledge many years ago. They ignored it then. I guess the proof is in the pudding."

Ontarians go to the polls in the province's 40th general election Oct. 6.