SALT LAKE CITY — A new legislative audit of the state's four-day workweek released Tuesday questions whether the switch is costing taxpayers more than it's saving.

The impact of working four 10-hour days a week on employee productivity is not being effectively monitored, and the savings were overstated, the report by the Legislative Auditor General's Office found.

But auditors stopped short of recommending dropping the two-year-old, Monday-through-Thursday schedule for most state agencies.

"We are not suggesting that we scrap the program," the audit's supervisor, James Behunin, told members of the Legislative Management Committee's audit subcommittee on Tuesday.

The report raised concerns about allowing employees to work during their commutes and from home, to exercise during the workday and to skip lunch in order to leave early, as well as other policies that could affect productivity.

"We cannot overstate the importance of guarding against weak policies and their potential for impacting employee productivity," the report states, urging changes.

That's because even a 1 percent decrease in worker productivity would cost about $15 million a year, according to the auditors, an amount that "significantly exceeds" the $1 million or so in savings they attributed to the shortened workweek.

When former Gov. Jon Huntsman Jr. imposed the schedule in July 2008 as a one-year pilot program, he promised the state would save $3 million annually on utility bills by shuttering offices on Fridays.

The savings on utility bills turned out to be about $500,000. Other savings that have been cited include $203,000 in custodial services, $4.1 million in overtime pay and some of the $1.4 million in state fleet costs.

But the auditors determined the actual savings attributable to the four-day workweek add up to less than $1 million. Other efforts by the state, including improvements to the management of heating and cooling systems, and cutbacks in using state vehicles, account for the lower costs, the report stated.

Lt. Gov. Greg Bell told the subcommittee the savings were "relatively modest and disappointing" but stood by the four-day workweek. Bell noted Utahns backed the 7 a.m. to 6 p.m. schedule in a survey ordered by Gov. Gary Herbert last year.

The lieutenant governor agreed the state should better monitor employee productivity.

"We need to do more. We need to do better," Bell said, adding that Herbert's commission charged with finding efficiencies in state government will offer recommendations by the end of summer.

The subcommittee's co-chairman, Senate President Michael Waddoups, R-Taylorsville, expressed disappointment about the expected savings from the switch falling short.

"That was my biggest concern all along, that we would not reach our financial goals," Waddoups said. "We have not seen the economic results we expected."

Bell told a reporter the audit could spark new interest among lawmakers in re-examining the four-day workweek, although he said the cost of moving back to a five-day schedule probably would stop them from taking action next session.

"It's just always been a topic," Bell said. "It wasn't popular with the Legislature when it rolled out, and there's been some concern the promised savings didn't materialize."

The report, too, took issue with the constitutionality of the schedule, noting the Utah Constitution states "eight hours shall constitute a day's work" by government employees.

In his written response to the audit, state Department of Human Resource Management executive director Jeff Herring said the constitutional issue already had been reviewed by the Utah Attorney General's Office, before the new workweek was put in place. Herring said the office would be asked to take another look.

Also Tuesday, a review of the state's career service system was released; it recommended Utah keep the current merit system with some changes.

Those changes include requiring new employees to be hired at will, a transition that already has been made in Texas, Florida and Georgia.

Almost two-thirds of the state's approximately 24,000 employees are under the merit system, intended to protect them from unfair personnel actions as a result of changes in political leadership.