WASHINGTON (AP) - More than two-thirds of the government's senior executives got special bonuses last year - nearly 4,800 workers - and several senators questioned whether a program designed to reward high performers is being used to simply boost salaries.

"It seems those who administer this bonus program at the various agencies think all the Senior Executive Service employees are above average," said Sen. Byron Dorgan, D-N.D., who is calling for an investigation from the Government Accountability Office.

The letter to GAO was signed by Dorgan, Sen. Daniel Akaka, D-Hawaii and Sen. George Voinovich, R-Ohio.

Government bonuses have been scrutinized since it was disclosed that Veterans Affairs officials involved in a $1 billion shortfall that put veterans' health care in peril got bonuses ranging up to $33,000.

According to a report from the Office of Personnel Management, VA career senior executive service members averaged $16,626 in awards in fiscal year 2006, with 82 percent of the VA's SES getting awards.

The average for VA senior executives service members was only second to the Nuclear Regulatory Commission, whose senior executives averaged $16,716 in awards. Almost 84 percent of NRC's senior executive service members received awards.

At some agencies, almost all of the senior executives received awards.

At the Office of Personnel Management, 97.2 percent of the senior executives got awards averaging more than $15,000, while 97.1 percent of General Services Administration senior executives averaged more than $12,000 in awards.

Over the 90 percent mark were also the departments of Housing and Urban Development (93.1 percent of senior executives averaging $11,000), Labor (91.7 percent at almost $14,000) and Defense (91 percent at almost $12,000.)

There were 7,137 SES members government-wide in fiscal year 2006. The OPM data showed that 67.2 percent of senior executive service members - nearly 4,800 - received awards between Oct. 1, 2005, and Sept. 30, 2006. The average award was $13,292.

Dorgan said the program was designed to reward exceptional or high performing employees. "I think taxpayers would agree, this is not how this program was intended to work," Dorgan said. "We need to figure out how it got so far off track and fix it."

Officials at the Office of Personnel Management said they had not seen Dorgan's letter and could not comment.

By law, 10 percent of the positions in senior executive service are set aside for appointment by the president. The other 90 percent are covered by the civil service.