HALIFAX - The Nova Scotia government is planning to ban bottled water in department offices, saying the move will divert plastic waste from landfills and help restore the image of municipal tap water.

Premier Darrell Dexter caught his own environment minister off guard with the sudden announcement, made during a speech before a convention of the Canadian Union of Public Employees in Halifax on Monday.

The premier told the union activists his office has sent a memo to officials in the Environment Department telling them to create a plan to ban use of the bottles where potable water is available.

Dexter later repeated his statement to reporters.

"The long and the short of it is this: where there is potable water in departments we will no longer use or provide bottled water," he said outside the legislature.

The premier said his office came up with the policy following a campaign by union and environmental groups calling for the bottled water ban.

"Bottled water generates tonnes of plastic that goes into the landfill. We want to stop doing that," said Dexter.

"We also want to support the well-run municipal water systems that exist here in the province and make the point that you can get, for pennies a glass, some of the highest-quality and best-tasting water anywhere."

The premier said the Environment Department will draft the details, including a check on where potable water supplies are available.

The premier said for the time being the initiative would only include government departments, but it's possible the measure could be expanded to other public buildings.

It's unclear whether the ban would extend to cafeterias, which may have contracts in place with bottled water companies.

Sterling Belliveau, the minister of the environment, said he hadn't been briefed by officials since the premier's orders arrived at his department late last week.

He told reporters he needed time to be briefed before commenting.

Opposition parties were critical of the way the plan was announced, saying Dexter had sidelined his own cabinet.

Andrew Younger, the Liberal critic for environmental issues, said he accepts the policy of banning bottled water but he wanted to know why Belliveau wasn't informed.

"What I have a problem with is he (Dexter) went directly to the deputy minister or somebody else in his department with a directive to ban water without going to the minister," he said.

"It's very clear here that the premier does not trust his ministers."

Conservative critic Chuck Porter said he also agrees with the policy, but said making the announcement to a union group before informing Belliveau was inappropriate.

"Maybe that's the way Mr. Dexter is going to run the show for the next few years. If that's the case, why does he have a cabinet?"

Meanwhile, the industry lobby group for bottled water said Dexter's plans will do little to keep the bottles out of landfills.

Elizabeth Griswold, executive director of the Canadian Bottled Water Association, said civil servants who consume bottled water are likely to turn to other packaged beverages.

"Bottled water competes with bottled beverages, not tap water. What you'll find is that people will turn to other beverages that are higher in sugar and higher in calories," she said.

"You're not solving a problem. You're adding to other problems."