Alberta's power-generating giant TransAlta has been accused of market manipulation again.

The power company is in trouble with the province's electricity watchdog — the Market Surveillance Administrator (MSA).

It says the company shut down some of its power plants on four occasions during peak periods in 2010 and 2011, driving up prices.

TransAlta rejects the allegations, but the case is already prompting calls for tougher regulation of the electricity market.

"I'm very disappointed to know that this is out there, but in terms of the fact that we have a deregulated system — we've got confidence in that system," said Premier Alison Redford.

The Wildrose Party's utilities critic isn't impressed.

"Disappointed? She should be outraged," said Rimbey-Rocky Mountain House-Sundre MLA Joe Anglin.

He stresses this isn't the first time TransAlta has faced allegations like this.

The company was fined $370,000 in 2012 for market manipulation.

Tougher penalties sought

Anglin wants to see tougher penalties.

"When they gouge the electricity market they become a predator on the economy of Alberta ... — seniors with fixed incomes, low income people and businesses struggling to get by."

TransAlta says the outages were for repairs and upgrades and has filed a complaint of its own against the MSA.

"We took this action because the MSA reneged from pursuing a promised formal stakeholder review process into offer behaviour for generating units subject to power purchase arrangements and because they have been attempting to regulate TransAlta and market behaviour retroactively, while at the same time investigating TransAlta in an aggressive and protracted manner, without clear rules having been established," said the company in a statement.

"We do not believe the MSA has followed due process in its role as the market monitor in Alberta."

The Alberta Utilities Commission will review the case.

"We have agencies in place to ensure that when these sorts of circumstances happen that there is the ability to investigate, to levy fines, to impose penalties and to ensure that it doesn't happen on a regular basis," said Redford.

Below is the request for a hearing submitted by the MSA, which outlines the allegations. On mobile? Click Here.