The chief economist of the U.S. Chamber of Commerce says the upcoming federal-military pay rise will add $60 to $100 to the average family's yearly tax bill and further inflate the wages of government workers who already make at least one third more than most other American workers.

The economist, Jack Carlson, a former interior Department official and deputy director of the Office of Management and Budget, says the 7.05 per cent October pay increase President Carter is considering is too much, and will put most private employers further behind Uncle Sam in the pay parade.

The 7.05 per cent increase Carter is expected to approve would go to nearly all white-collar federal civilian workers and military personnel. It will cost about $3.5 billion and is designed to make them "comparable" with wages and wage changes in the private sector.

Carlson says the comparability machinery isn't working properly. He said the government simply adds big percentage raises each year without considering true wages and fringe benefits outside government, or in state and local governments.

The Commerce Department, Carlson says, reports that "average pay for a full-time equivalent employee in the private sector was $11,840 last year compared to $16,201 for the average civilian government employee."

Carlson, who conceded that some of his old friends in government "might get mad at him," said average federal pay exceeds pay in "52 of 59 industries listed in the Department of Commerce's publication (the July Survey of Current Business') . . ."

The former federal official said fringe benefits in government - especially retirement and leave - are generally better than industry and that the actual total cost of a 7.05 per cent pay riase would, in fact, be greater than 10 per cent.

Carlson said he believes that one reason living costs are so high in Washington is because the federal government feeds them by being such a generous employer. More than 350,000 people here work directly for Uncle Sam, and there are nearly 70,000 military personnel and about 70,000 federal-military retirees in the Washington area.