A federal judge refused yesterday to allow an official of the National Right to Work Committee to take sworn testimony from the AFL-CIO as part of a suit challenging procedures of the Federal Election Commission.

U.S. District Court Judge Charles R. Richey ruled that forcing the AFL-CIO to give testimony "would involve unwarranted intrusion into the political activities of the organization and such intrusion may well curb or otherwise interfere with the organization's legitimate political activity" and thereby violate the First Amendment protection of free speech.

The suit was brought by National Right to Work Committee official Henry L. Walther.It challenges the election commission's exemption of the AFL-CIO from a provision of the federal law designed to prevent groups from evading limits on contributions to candidates.

Richey ruled last week that the FEC had no legal basis for the exemption. The suit now will go forward to determine whether the AFL-CIO has violated the law by making contributions to candidates through political action committees of member unions as well as through the national organization.

The committee announced last week, following Richey's decision, that it intended to uncover through discovery proceedings in the suit the relationship between the national AFL-CIO contributions and donations from local unions around the country.