President Carter's plan to introduce paid parking at federal buildings has a Catch-22: It may reduce the number of bureaucrat commuter cars and car pools on the road, but boost the number of VIP vehicles used daily.

Ironically, the proposal to democratize parking in government exempts VIPs who rate air-conditioned cars and drivers. They will not have to pay the $25 average monthly tab that will hit 27,000 less-affluent federal parkers here in October.

New regulations due soon will implement phase one of the great parking exercise. Feds who now park free, or in cheapie, subsidized spots, will have to start paying half the equivalent commercial rate this fall. By October, 1981, they will pay full fees which - based on downtown private charges - range from $40 to $90 per month.

In his April energy message, President Carter noted that it was unfair for taxpayers to subsidize bureaucrats with free parking, and he decided to end it for "everybody." In this case, however, everybody isn't everybody.

About one-third of the best free parking spots in town will not be hit by the president's horder. Members of Congress and congressional employees will still have several thousand reserved parking spaces at the office. Free parking spaces - subsidized by the taxpayers - will cointinue at National and Dulles airports for members of Congress and the Supreme Court.

VIPs, from cabinet departments, independent agencies and the White House itself iwll not have to pay any parking fees if they use government transportation. Several hundred cars - air-conditioned, with telephones and reading lights - are available to VIPs who are deemed too important to the republic to drive, walk or bus to work on their own.They will park free.

VIPs who, for one reason or another, drive themselves - and some do, just like real folks - will be charged for parking in October. Hence the president's plan may reduce the number of commuter cars used by feds, but it will probably increase the number of VIPs who require home-to-office pickup and delivery.