Newfoundland has called for a judicial inquiry to find out why more than 300 breast cancer patients were given wrong test results, possibly leading to incorrect treatment.

The independent commission will be established by the provincial cabinet under the Public Inquiries Act.

Health Minister Ross Wiseman said it's important to determine how the tests were botched so it never happens again.

"In the interests of openness and transparency, we feel that this is the only way to be able to make a full public disclosure of what exactly took place here, and more importantly, what can we learn from this," Wiseman told a news conference.

The N.L. cabinet has not yet appointed a commissioner to lead the inquiry or set the terms of reference for the probe.

George Tilley, CEO of the Eastern Health Authority, apologized on Friday for the incorrect testing.

In 2005, the Eastern Health Authority asked Toronto's Mount Sinai Hospital to review 2,000 hormone receptor tests dating back to May 1997, after oncologists found conflicting results in breast tumour samples.

Hormone receptor tests determine if a patient is estrogen- and/or progesterone-positive, in which case they may benefit from hormone therapy like Tamoxifen.

According to an affidavit filed in the province's Supreme Court and signed by the authority's risk management consultant Heather Predham, 763 women were given the tests.

Of that number, 317 received the wrong result. But only 117 were alerted about the mistakes, because their treatment was changed.

"I regret the decision that we didn't simply refer to it earlier,'' said Tilley. "And I apologize for the confusion that that caused."

At least 26 of the women who received the wrong test results have died, although it's unclear whether their deaths were directly related to their cancer.

Meanwhile in the House of Assembly, opposition parties reacted to news of a judicial inquiry by demanding assurances that the inquiry will investigate not only the Eastern Health Authority, but the government's role in the matter as well.

"There are six key items that you have currently identified in your  (that) detail solely and only with the involvement of the testing, vis a vis, the Eastern Health Authority," said Liberal justice critic Kelvin Parsons.

"I say to the (health) minister that this issue goes beyond that, and in particular, it concerns the issue of was there and was there not any involvement or knowledge ... of officials in the department of health, including the minister of health?"

Wiseman promised the commissioner of inquiry will have broad powers.

"No intent here at all, none whatsoever on the part of this government ... to restrict what the commission and what they want to do to ensure that they get the answers to the people of Newfoundland and Labrador so all of us ... will fully understand what happened with respect to ER and PR testing," said Wiseman.

With reports from NTV News and files from The Canadian Press