Alberta PC leadership candidate Thomas Lukaszuk says he's sorry he didn't check into the details of his data plan but is defending a $20,000 cellphone bill that taxpayers footed while he was on a private trip.

The bill, which was for overseas data and roaming charges, was incurred while Lukaszuk was in Poland and Israel in October 2012. The cellphone bill information was leaked to the Edmonton Sun.

In a statement emailed on Monday, he said the trip was made on his personal time and that he covered his own travel costs.

But Lukaszuk said he continued to work on government business while out of the country.

"I was deputy premier [at the time], and there really isn't 'private time,'" he wrote. "I was expecting to do some government work while I was away (reading and answering emails, reviewing briefings, and staying current with Alberta and Canadian news), so I took my equipment with me."

Lukaszuk believes that the information was leaked internally in a bid to damage his reputation two weeks before the leadership vote on Sept. 6.

"You know, this wasn't new information," he said. "It was previously available but obviously it's being strategically used at this point in time."

He told CBC News the premier's office asked him to handle a legal matter. The high cost came from downloading secure documents from an Edmonton law firm.

"There were a lot of long conversations, and proceedings with lawyers and the courts," he wrote.

Lukaszuk did not specify what case he was working on, saying only it was under a court-ordered publication ban.

"It was put on my lap for me to deal with by the premier's office using 3G for two reasons," he said on Monday.

"A: mostly where I was, there was no Wi-Fi and B: Wi-Fi wasn't a secure way of transmitting documents."

Lukaszuk said he tried to negotiate with service provider Telus over the bill but "they told us to take a hike." Since then, the province has negotiated an improved contract with Telus.

As for Lukaszuk himself, he said he personally switched providers as a sign of protest. He said he has since ensured a data plan is in place whenever he travels abroad.

"Absolutely, I made a mistake, and for that I apologize. I did not check the data plan myself, and I did not confirm that my office had done so. The result was that accomplishing a task cost the government more than it should have. This was an expensive lesson."