For three years as a United Press International reporter in Washington, Donald Lambro has poked his nose in the city's bureaucratic corners on a one-man search-and-destroy mission against government waste. Among other things, he knows:

How much taxpayers fork over so congressmen can enjoy massages in their private Capitol Hill gyms (about $100,000 annually are paid in salaries).

What it costs to fix fancy meals for cabinet members (more than $361,000 a year).

Why some federal employes earn more than the vice president (they pyramid military and civilian service pay and retirement benefits shrewdly).

Nevertheless, Lambro says he knows about only a fraction of the money wasted by government, an unsettling admission in his new book, Fat city, that lists 150 programs and agencies he thinks ought to be hit by the budget-cutter's ax.

"Things are a lot worse than I thought," Lambro says of his findings since 1975 when he first wrote a book, The Federal Rathole, that listed only 50 programs and agencies he considered worthless. "There used to be a general feeling that there's a certain amount of waste in anything the size of the government, but it should be tolerated for the greater good."

Today Lambro welcomes with pen and open notebook what he perceives as a new era of disgust with government malfeasance and waste. Words such as "outdated," "extravagant," "wasteful" and "ineffective" roll easily off his tongue.

The son of a Wellesley, Mass., barber, Lambro first came to Washington in the late 1960s to edit a magazine published by the Young Americans for Freedom. After a series of writing jobs, UPI hired him for its Hartford bureau and moved him to Washington in 1970.

Lambro, 38, acknowledges his political conservatism, but says that didn't spark his interest in government money matters.

"My suspicion all along has been that the government takes too much of our money and wastes too much of it," he says. "It is a story of large proportions, but the news media weren't covering it."

So three year ago UPI's Washington bureau chief, Grant Dillman, assigned Lambro to write a continuing series called "Watching Washington." Bureaucrats began dreading Lambro's calls, as he examined the way consultants billed government clients, how civil servants waste money on travel, and the growth of government self-promotion through expensive films, ads and brochures.

"He's very thorough, very fair," says Dillman, who has taken some heat from bureaucrats who didn't like Lambro's writings.

"We report an agency's formation and their handouts, but we don't go back and hold them accountable," answers Lambro, who doesn't mind one bit the screams of skewered workers in the fat city.