Twenty-nine senators, including Sen. Robert J. Dole (R-Kan.) and seven other Republicans, have written President Reagan, urging him to delay for a year the implementation of new regulations for this year's Combined Federal Campaign.

A similar letter is circulating in the House, where it has garnered more than 70 signatures.

The new Office of Personnel Management regulations are controversial, not only because they were issued almost six months late but also because they seek to bar environmental, minority, women's and legal defense groups from receiving money through the federal employes' annual charity drive.

That move was embodied in an executive order limiting the campaign to charities that provide direct health and welfare services. The order specifically excluded groups that engaged in lobbying, advocacy or political activity.

Because the regulations have been issued so late, the campaign is unlikely to be able to meet its scheduled Labor Day kickoff, and charities and organizers fear that it may be so delayed that it will compete with traditional holiday charity drives.

In the senators' letter, they express the fear that "the confusion and controversy generated by last-minute efforts to revise the eligibility rules will inadvertently harm private charities and impede the entire voluntarism movement. Fortunately, you can rectify this problem by adopting last year's rules."

A White House spokesman said Reagan had not read the letter.