David Broder's "Thatcher: Doing So Much With So Little" {op-ed, June 24} sneers at the "antic British electoral system" because it permits a 43 percent electoral plurality to achieve a large majority in Parliament, especially when three parties are competing. Whether this is undesirable and undemocratic is debatable. Certainly the British people have consistently rejected the proportional representation system that wrecked the Weimar Republic and that, even in the German Federal Republic, threatens paralysis of decision-making by encouraging multiple parties, including such eccentrics as "the Greens."

But what takes my breath is Mr. Broder's assumption that the British operational system is somehow abnormal. Has he looked at the American system? At the Electoral College? At the gerrymandered congressional districts? Does he know that 53 percent of the potential electorate voted in the presidential election in 1984? And that only 37 percent voted in the congressional elections of 1986? Does he realize that the Democratic majority in Congress today -- the majority that is out to reverse the 1984 decision -- represents at most about 20 percent of the potential voters (not to mention the House's gerrymandered products)?

Successful democracies should think twice before stoning other people's glass houses!

RAYMOND ENGLISH Vice President, Ethics and Public Policy Center Washington

I was amused by The Post's London correspondent's use of one of the standard boilerplate phrases of British political journalism, the "peculiarities of Britain's 'first past the post,' winner-take-all electoral system," in her analysis of the recent election. Since the British system is the very one used in our country to elect every state legislature, both houses of Congress and the Electoral College, it should not seem peculiar to most readers. Moreover, such a system appears to provide the only democratically legitimate way of choosing a legislature in which each member represents a specific geographical district.

Some countries have adopted systems, no doubt equally legitimate, in which legislators are not so specifically linked to districts, thereby enabling smaller political parties to be represented in government. Irrespective of the merits of any such system, its adoption in Britain (or here) would evidently involve a major constitutional change, not some minor administrative concession by the two main parties. Such a change would necessarily dilute the power of every individual member of Parliament, and therefore is unlikely to happen in the absence of gross abuses of the current system. CHARLES CLARK Wheaton