A group of businessmen serving as a presidential advisory panel yesterday released its third batch of cost-cutting reports, recommending changes in management of government hospitals, real estate holdings and construction projects that it says could save nearly $26 billion over three years.

As with its previous reports, the President's Private Sector Survey on Cost Control said that its proposals involve management improvements, not policy changes.

However, nearly all of the $3.7 billion in savings it identified at the Labor Department would require amendments to laws administered by the department. Savings in federal construction projects would rely heavily on "changing various environmental procedures and requirements."

The task force report on construction management listed $5.4 billion in savings, and said that some of its recommendations would entail changes in the Clean Water Act, the Wild and Scenic Rivers Act and the Safe Drinking Water Act.

The private-sector panel was established by President Reagan last June to find ways to cut government spending. Its 161-member executive committee and 1,300-member task forces have put together 38 reports on government departments and agencies.

Five reports were released yesterday, bringing to 16 the number that have been made public.

Among the reports released yesterday was one on the Veterans Administration, where the task force identified $3.1 billion in potential savings, about half of that from changes in claims processing.

A document from one of the VA task force members, made public by an angry congressman in March, suggested the survey would recommend abolishing the VA. The survey's chairman, industrialist J. Peter Grace, yesterday characterized that document as an "obsolete and rejected letter," and said the panel had never contemplated such a step.

In its hospital management report, however, the survey suggested that the government could save $8.5 billion by integrating the hospital systems run by the VA and the Army, Navy and Air Force.

The report said the occupancy rate in Defense Department hospitals is 46 percent, while private hospitals plan for an 80 percent occupancy rate. The armed forces' separate systems leads to "a disproportionate number of underutilized hospitals," the report said, and it recommended freezing construction and renovation funds for 47 military hospitals.