Fund-raisers for the Reagan-Bush campaign, anxious to tap the affluent metropolitan Washington area, are making a big, big mistake when they try to put the bite on any of the 340,000 U.S. workers here. Reason: The White House (occupied by you-know-who) has told feds not to give any money to the Reagan-Bush campaign.

A number of government employes have complained that they have gotten letters and telephone calls from the president's campaign committee asking for funds. "When I tell them I am Hatched, they say, 'What are you, a chicken?' or otherwise start with the jokes," an employe said yesterday.

Being "Hatched" means that the worker -- like most of the government's 2.8 million career civil servants -- is covered by the Hatch Act, a 1939 law that prohibits feds from taking active roles in partisan political campaigns, and protects them from arm-twisting by their political bosses. Retired federal workers, and the spouses or family members of feds, are not covered by the law.

The Hatch Act does not prevent federal workers from registering or voting or expressing political opinions as private citizens. The minimum penalty for a Hatch Act violation is a 30-day suspension without pay.

Earlier this year the White House sent a memo to agency heads, advising them to warn their employes not to give to the Reagan-Bush campaign. It did not say anything about feds giving money to the Mondale-Ferraro ticket, or to other political campaigns.

While most federal workers got the word, it appears that some Reagan-Bush fund-raisers have not. The memo, from Fred F. Fielding, counsel to the president, pointed out that the Hatch Act makes it illegal for employes to give money to "any other officer or employes of the U.S. who is the employer or employing authority of the contributor. Although this issue is not free from doubt, this provision may prohibit any federal employe from contributing" to the Reagan-Bush campaign.

The White House directive said "prudence requires that any ambiguity in the language of this statute be resolved against placing any presidential appointee or other federal employe in the position of inadvertently violating federal law. Hence, in the absence of any judicial interpretation of this provision . . . all federal employes should be advised that this statute may preclude them from contributing to Reagan-Bush '84, the authorized campaign committee of the president.

"I regret that such advice may inhibit federal employes from the full exercise of their First Amendment rights; nevertheless, in the interest of maintaining strict compliance with all federal statutes, every federal employe should be made aware of the language and the potential restrictions of this statutory provision."

So if you are a fed, and a Reagan-Bush fund-raiser calls on you, tell them your boss -- and their boss -- says it is not a good idea. If they persist, tell them they can take it up with Fred, at the White House.