TORONTO - The battle over planned changes to Ontario's prescription drug system heated up Monday, with pharmacists and the government squaring off over claims that the industry wants to "hold patients hostage" by withholding services.

"This is a fight between big pharmacy and the government of Ontario," said Health Minister Deb Matthews.

"We have seen indications that they may start putting patients in the centre of this and I want assurance from them that they will not do that."

A coalition of pharmacy associations promptly shot back that it did not condone pharmacists withdrawing services, but added the amount of services they can provide will be reduced over time if the changes go ahead.

The group issued a terse response to a letter from Matthews in which she took issue with reports that pharmacies temporarily withheld services the day the changes were announced last week.

Calling Matthews' statements "inflammatory in tone and inaccurate in fact," the group said her message was "hardly in keeping with our desire for an ongoing, respectful dialogue we are hoping to continue concerning the proposed cuts your government is initiating to front-line patient care in Ontario."

Nadine Saby, president of the Canadian Association of Chain Drug Stores, said the government needed to accept some responsibility for possible closures.

"How can a reasonable individual think that you can take three quarters of a billion dollars out of pharmacy care and not have it affect the provision of that care in some way?" she said.

At the same time, Shoppers Drug Mart upped the ante by announcing just hours after Matthews' letter surfaced that it will start the first in a series of reductions in store operating hours as a result of what it called funding cuts to pharmacies.

Starting Tuesday, the giant drug store chain, which has said it strongly opposes the changes, will cut store hours for seven locations in the London region -- Matthews' riding.

Two of the London stores will also implement what is known as "lock-and-leave," which will see the pharmacy closed while the rest of the store remains open.

Saby declined to comment on Shoppers' decision, but said the group was looking at whether the minister had libelled or slandered the profession in some of her comments, and would be speaking to people around the province about what the changes may mean for them.

While pharmacists said they hoped the government would reconsider some of its plans, Matthews said that option wasn't on the table.

The changes will lower the cost of generic drugs by 50 per cent and clean up abuses when it comes to professional allowances -- payments generic drug companies make to pharmacy owners for stocking their drugs, she said.

Professional allowances are intended to fund patient services, but the government claims they are instead being used by many pharmacies as rebates to fund fringe benefits, bonuses, overhead costs and boost profits. The funding amounted to $750 million reportedly paid to pharmacy owners by generic drug manufacturers in 2009.

"I'm sure you would agree that to deny public access to needed medicines as a point of leverage in a policy dispute with the government is simply irresponsible," Matthews wrote in her letter to Ontario Pharmacists' Association, the Canadian Association of Chain Drug Stores and the Independent Pharmacists of Ontario.

"I would therefore ask you to please confirm that pharmacies, including big drug store pharmacy chains will not hold patients hostage to your disagreement with government policy."

Matthews also said some industry leaders have been misinforming the public and scaring patients unnecessarily, and added she's concerned about claims that pharmacies will have to cut back on services like blood pressure checks.

The minister didn't say what action the government might take if pharmacists don't heed her warning, saying only that at this point she is appealing to their professionalism.

Progressive Conservative Leader Tim Hudak said threatening pharmacists was the wrong move.

"I don't see how it's going to help a senior citizen, a sick individual trying to get care from the pharmacist when Dalton McGuinty is seen to be going to war with the neighbourhood pharmacist," said Hudak.

New Democrat Andrea Horwath, meanwhile, said she supported steps toward cheaper drugs, but was worried about what fewer pharmacies could mean to already under-serviced communities.

"I'm hearing from all my northern members that there's a concern that dispensing fees are going to increase significantly ... or the lack of pharmacies will mean that they don't have access to pharmacies in the same way as other Ontarians," she said.