Full Idea
Hare has proposed that utilitarianism is the ultimate standard to which we are led by the categorical imperative.
Gist of Idea
The categorical imperative leads to utilitarianism
Source
report of Richard M. Hare (Freedom and Reason [1963], p.123-4) by Thomas Nagel - Equality and Partiality
Book Reference
Nagel,Thomas: 'Equality and Partiality' [OUP 1995], p.44
A Reaction
It seems to me better to say that Kant starts (unwittingly) from something like utilitarianism, that is, an assumption that human happiness and welfare have some sort of intrinsic value that cannot be demonstrated. Otherwise evil can be universalised.