The Metropolitan Police's Commercial Vehicle Education Unit, which has run since 2005, will close in March 2010.
Currently, TfL finances the £1m-a-year scheme, which aims to educate cyclists on the blindspots lorry drivers encounter, and to talk to haulage firms about cyclist awareness. Three police sergeants and nine constables are employed on the initiative.
"This is a huge backward step for the safety of cyclists and pedestrians in London. The Mayor is risking Londoners' lives in order to save a small amount of money. TfL can talk to haulage firms, but these officers have special legal powers either to persuade them to improve on safety, or make them," says Jenny Jones, a Green Party London Assembly member.
A TfL spokesman says other similar educational schemes will be undertaken.
Johnson himself had a lucky escape in May when a truck nearly dragged a car into the path of his bicycle.
Last year, nine cyclists were killed in collisions with HGVs on London roads.