Johnson made the statement during a speech to delegates at the Conservative Party Conference in Birmingham.
In a signal to the Tory right, the mayor said he would like to go further than George Osborne, who lowered the top rate from 50p to 45p in the budget, reported the Guardian.
Johnson also used the speech to stress his loyalty to the prime minister and indicated he would serve a full four-year term as mayor.
There has been speculation that he might stand in the 2015 general election to place him in pole position to succeed Cameron as Tory leader.
Giving his backing to the government’s austerity programme, he drew on the success of the “can do” attitude of the Olympics to take the country forward, with British firms becoming “gold medal winners”.
