Boston ? Gov. Mitt Romney asked the state’s highest court Tuesday if he has the power to fire the Massachusetts turnpike chairman after an engineer who led an investigation into leaks at the $14.6 billion Big Dig project says he can no longer vouch for the safety of its tunnels.

“With the Big Dig there’s been a pattern of cover-up and stonewalling that has left the public with little confidence that the project is being managed well or that the road and tunnel system are safe to travel,” Romney said.

But he stopped short of calling the tunnels unsafe and said he would continue to drive through them.

The governor’s comments came in response to a March 9 letter written to the Turnpike Authority by engineering specialist Jack K. Lemley, who said he was “unable to express an opinion as to the safety of the I-93 portion of the Central Artery.”

Romney has previously called for Turnpike chairman Matthew Amorello’s resignation. In his request to the state Supreme Court, Romney wrote that Amorello has “failed to discharge the critical duties of his position competently” and is “presently threatening the public good.”

Amorello defended the safety of the tunnels Tuesday and said he has no intention of resigning. “If there was ever a hint that public safety is in jeopardy, I promise you we would close the tunnels immediately,” he said.

The Big Dig highway project, which buries Interstate 93 under downtown Boston, has been plagued by cost overruns and riddled by leaks and other construction flaws.

In September, water broke though a faulty wall panel and flooded one of the tunnels, backing up rush-hour traffic for miles. A subsequent investigation headed by Lemley found hundreds of smaller leaks.

Lemley told lawmakers in November that there was no risk to people driving through the tunnels. Since then, Big Dig officials have identified more than 40 sections of the tunnel with problems.

In his letter, Lemley said project officials would not provide records and data on the new problems. He said his change in position also was driven by the apparent lack of any formal plan by Big Dig officials to address the leaks.

Romney also Tuesday ordered an independent review of the Big Dig’s safety by the state highway department and said he would ask the state’s attorney general to immediately seize any Turnpike documents related to the safety of the tunnels.