EDMONTON -- Alberta Justice Minister Doug Schweitzer passionately defended the head of Alberta's oil and gas inquiry after the NDP asked whether he broke conflict of interest rules in granting a contract to his son's law firm.

In a meeting of the Standing Committee on Families and Communities, Schweitzer addressed the controversy surrounding Steven Allan, who is heading up the public inquiry into whether foreign interference is affecting the province's oil and gas industry.

"This person has had an immense amount of success in their career," said Schweitzer. "How he's been dragged through the mud over the last few weeks has been appalling. And the fact that the NDP lines of attacks on this is the same as ecojustice is appalling, absolutely appalling in what we are seeing and the attacks on this person's credibility.”

It was revealed last week that Allan hired Calgary Law firm Dentons on a contract worth more than $900,000 for legal advice. His son, Toby, is a partner at the firm.

That prompted the Opposition NDP to call for an ethics commissioner probe into the hiring, which was denied as the commissioner does not have jurisdiction in the matter.

Premier Jason Kenney and other party members have denied that there is a conflict of interest, with Kenney saying he had been advised by public service there was no conflict.

"Commissioner Allan in his role is akin to a judge," Schweitzer said Tuesday. "He’s free to conduct his inquiry as he sees fit. His decision to hire who he sees fit, to assist him in the inquiry is built right into the terms of reference, and built right into his agreement. I just leave it at that."

In response, NDP MLA and ethics critic Heather Sweet pressed Schweitzer and the government to be more transparent about the $2.5-million oil and gas inquiry. She also said questioning the government about its spending is not the same as attacking Allan.

"This is not about [Allan's] expertise or his ability to do the job, and I've been very clear with that," she said. "The questions that have been asked specifically around the $2.5 million, which is something you have commented in the media about how it went through your ministry to clarify whether or not there would be a conflict of interest, the concern is that there is a perception that there's a conflict of interest."

She said Albertans have a right to know exactly what the $2.5 million is being used for amid budget cuts that have public servants throughout the province concerned and frustrated.

"it is a question needs to respond to."

Schweitzer didn't respond to Sweet's questioning, saying the $2.5 million budget for the inquiry is under the jurisdiction of the energy ministry.

"I've already made my statement clearly," he said.

The NDP has asked the energy ministry if it did its due diligence to determine there was no conflict of interest.

Correction: An earlier version of this article stated the contract awarded to Dentons was $2.5 million. This is incorrect. The contract was actually worth $905,000.