BEFORE LEAVING for the Grand Old Party's party in Detroit, Prince George's County Executive Lawrence J. Hogan came up with a nifty little way to get off a publicly financed parting shot at the Democratic county council of which he is so unfond: all property owners, in fact, received a copy of his political poke at the council -- because Mr. Hogan slipped it into the 1981 tax-bill mailings. But since this joke was at the expense of the council members as well as county taxpayers, Mr. Hogan is getting rapped for his action -- by many who surely protest too much.

What the county executive did was include with the bills an in-partial-depth analysis of the various taxes people have to pay in the fiscal year that got under way this month. On the flip side was a special message from Mr. Hogan explaining some more fiscal facts and noting that the council has approved an increased tax rate for water, sewer and park services "over my objections." What angered several council members, apparently, was Mr. Hogan's failure to give them credit for cutting the property tax further than he had proposed. In other words, it's all right to insert an editorial in the tax bills as long as it is even-handed in its praise.

But wouldn't most taxpayers prefer not to pay for political messages in what amounts to bad-news mail from the government in the first place? At least the council members knew enough not to get too holy about Mr. Hogan's use of the county mails for political purposes -- since he's not the first to do so; it was Mr. Hogan, after all, who charged that his predecessor, Democrat Winfield M. Kelly Jr., was misusing taxpayer money to send out glossy pamphlets with county tax bills. Now it is Mr. Hogan who is saying that, as result of his latest message, "dozens of people have been calling to tell me how happy they are with the tax cut and how wonderful I am."

Lest anyone get the wrong impression, this is not a practice limited to Prince George's or even to Maryland. Perhaps you may have noticed that all of a sudden there is more franked-mail "news" that your member of Congress has decided to share with you; the letters from and about Walter Fauntroy, Michael Barnes, Herbert E. Harris and Joseph Fisher do tend to arrive more frequently in even-numbered years. Just because Mr. Hogan is in the midst of an off-year is no reason to single him out; the only difference in using a tax bill is that the recipients can't just mark it "Return to Sender" without throwing in a contribution for their government's coffers.