A major Alberta power company has been issued a $370,000 fine for manipulating power rates.

TransAlta has agreed to pay the fine, which was issued on Tuesday.

According to an agreed statement the company blocked the sale of cheap hydro power for 31 days from B.C. last year.

Documents have shown the move by TransAlta drove up the cost of power, which brought in an extra $245,000 for the company.

A spokesperson with the Alberta Utilities Commission said TransAlta's move broke the rules in the Alberta Utilities Act.

"There's a requirement here in Alberta of market players to act in a manner that creates a fair, efficient and openly competitive market place," Geoff Scotton said.

"The suggestion here is that activity may have occurred that did not work in that manner."

However critics wonder if the company has learnt its lesson.

"This is the first time that we've really caught somebody," Wildrose MLA Paul Hinman said.

"Now the question is how many times has it occurred in the past? How much money have they really pocketed?"

But the Premier said the fine proves the system works.

"We have systems in place that allow us to get to exactly this point," Premier Alison Redford told CTV News.

"If these are the circumstances that have been determined by the fact-finder, that's a good thing."

The fine will be formally laid after the Commission approves the joint submission.

"All of that application needs to be scrutinized by the Alberta Utilities Commission and by a panel of commission members," Scotton explained.

The money will go into provincial coffers.

With files from Bill Fortier