Premier Ed Stelmach has issued an apology to provincial opposition parties after their leaders were barred from a news conference at an Alberta government building.

On Thursday, both Liberal Leader David Swann and NDP Leader Brian Mason were not allowed into Government House in Edmonton while Health Minister Ron Liepert was holding a news conference to unveil a new prescription drug coverage plan for seniors.

A security guard told the politicians they were not allowed inside at the order of the minister.

On Friday, Stelmach said that was wrong and should not have happened, adding he intends to send a message to his cabinet ministers at a meeting on Tuesday: Opposition members are allowed to attend news conferences and should not be stopped from doing their jobs.

While he accepts the premier's apology, Mason said he wants to hear it from Liepert.

"What happened when I was physically prevented from entering a minister's news conference announcing a key area of policy that I've been working on is it showed that Mr. Liepert, at the very least, has real contempt for the role of the opposition," Mason said.

"But I believe our role is very important in our democracy, and that is to hold the government to account."

Mason also wants to put the issue of opposition members' rights to the Speaker of the house, Conservative MLA Ken Kowalski.