It's a familiar sight in Canberra during a sitting week: the long lines of white COMCARS waiting patiently outside the entrances to Parliament House.

The fleet of shiny sedans ferry MPs and Senators wherever they need to go, including to and from home, out to dinner or to a function. They also wait outside Canberra airport at the start of a sitting week, in a cross between a taxi rank and a personal limo service.

But one of the most treasured pollie perks could be on the chopping block, with an independent review finding the so-called COMCAR "shuttle service" - the lines of cars outside Parliament and the airport - is not good value for taxpayer's money.