Best said developers might simply pay the tariff and leave councils with responsibility for ensuring the funds were spent on social housing on a different site.
"Funds raised by tariffs might not find their way into affordable housing at all, as associations may find it impossible to buy the land they need," he added.
Best, a former chief executive of the National Housing Federation, argued that although the present process of section 106 agreements, was "flawed", he believed it was "improvable". Section 106 currently provides around 12,000 homes a year.
Best also said that the deficit between the amount of affordable housing being built and what is required would "only be made good by institutional investment in a new-look private rented sector and public investment in affordable housing, mostly through the Housing Corporation".