Transport for London workers should lose the free travel passes that they are allowed to give to family and friends, Conservatives in the capital have argued.
Workers are allowed to nominate one person who they live with, who can take advantage of free travel across the capital.
But a study by Tories in the Greater London Authority found the freebies cost the government £22m ($34m) each year after recipients made millions of journeys on London's transport network using the pass.
According to the party's "Free Ride" report released on 26 May, 3.6 million Tube, DLR and tram journeys were taken in 2014 along with 4.8 million bus journeys by pass holders.
It predicts the cost of such journeys could reach £111m by 2020 and claims it is a waste money that could be spent on giving free travel to firefighters, bringing their transport benefit in line with police officers in the capital.
Andrew Boff, leader of the Greater London Authority Conservatives, said: "At a time when the public sector is having to make money stretch further, there is no justification for individuals who do not provide an essential role in keeping London in operation receiving these types of benefit."