NASHVILLE -- Republican gubernatorial candidate Bill Haslam came under fire from two GOP rivals Thursday for his refusal to release income tax returns.

U.S. Rep. Zach Wamp, R-Tenn., and Shelby County District Attorney Bill Gibbons stepped up their previous criticisms during a gubernatorial candidates' forum hosted by the Tennessee Press Association and The Associated Press.

Mr. Haslam's two rivals say he should detail how much money he makes from Pilot Corp., the national truck stop chain that he and relatives own.

The mayor of Knoxville, Mr. Haslam today begins what opponents say is a $1 million statewide television and radio ad blitz that highlights his previous experience as a Pilot president when it comes to creating jobs.

Rep. Wamp, a Chattanooga congressman, and Mr. Gibbons pounced on Mr. Haslam in response to a question posed to candidates about their support for governmental openness and transparency.

"He has a TV ad out claiming to be the man from Pilot Oil. Yet he wants to keep his Pilot Oil income a secret," Mr. Gibbons said.

Unlike the other three Republican and three Democratic gubernatorial candidates, Mr. Haslam has declined to release his income tax returns or reveal how much he earns from Pilot, a privately held companyh.

Mr. Haslam previously has said doing so would disclose information about other family members' income as well as information about the company. He said Thursday that people know he is part owner of Pilot.

"(It) bothers me to hear somebody say a Tennessee company that started as a small business, that's grown to be a national company, that there's something wrong with that," said Mr. Haslam, who appeared somewhat surprised by the sharpness and directness of the attacks.

Earlier, Rep. Wamp said both he and Mr. Gibbons had "gone way beyond" the three years of federal income tax returns sought by the Tennessee Newspaper Network, a collaborative effort of the state's four largest newspapers, including the Chattanooga Times Free Press.

Mr. Haslam, meanwhile, provided a summary of income and taxes paid, excluding any income from Pilot.

"On Wall Street they say too big to fail," Rep. Wamp said. "I wonder here if one family or one corporation is too big to be held accountable like everyone else. ... Where is this money coming from that pays for million-dollar TV buys? Who are you in partnership with? Who might stand to make money from you being governor. That's transparency. It starts now."

Mr. Haslam replied, "I guess leave it to somebody who's been in government all their life to confuse a question about public government records with an individual record.

"That being said, I think it (Wamp's remark) is referring to a TV buy," Mr. Haslam said. "It's real obvious that came from 7,300 different contributors who put the money into our campaign to support us."

Mr. Gibbons later said he was "astounded" by Mr. Haslam's refusal to release his income tax returns and pointedly said to him, "Just tell us your income from Pilot Oil, right now."

Others participating in the forum were Lt. Gov. Ron Ramsey, R-Blountville;Sen. Jim Kyle, D-Memphis; former state House Majority Leader Kim McMillan, D-Clarksville; and Jackson businessman Mike McWherter, a Democrat.

Times Free Press Executive Editor and Publisher Tom Griscom moderated the debate.