The State Department wastes tens of millions of dollars a year on premium airline tickets, congressional auditors said Monday.

About two-thirds of premium tickets — mostly business-class — were not properly authorized nor justified, the Government Accountability Office said.

Also, while federal agencies are authorized to recover payments to airlines for unused tickets, the department paid for about $6 million in tickets that were not used.

The GAO said there was a breakdown in controls and ineffective oversight and recommended several changes, including required audits of premium-class travel.

The report covered the period between April 2003 and September 2004. It found department accounts were used to purchase more than 32,000 premium-class tickets costing nearly $140 million.

This amounted to about half of the $286 million spent on airline tickets.

Many of the authorizations for the purchases were signed by subordinates who told the GAO they could not challenge the use of premium-class travel by senior executives.

"Because premium-class tickets typically cost substantially more than coach tickets, improper premium-class travel represents a waste of tax dollars," the report said.

At the State Department, spokeswoman Julie Reside said the report had overstated the nature and extent of the problem.

However, Reside said the department was "firmly committed to aggressive stewardship of the taxpayers' resources with which we are entrusted."

And, she said, "we are resolute in our commitment to remedy the deficiencies the GAO noted."