Should we increase spending on preventative medicine?

On 3 April Yesterday Life Matters interviewed Jeremy Sammut from the Centre For Independent Studies . He's been studying reports of the outcomes of public health campaigns and has concluded that there's a big difference between knowing what to do and doing it.

The CIS has written an article on six social policy myths. One of the myths they challenge is that higher spending on preventive medicine will reduce health costs in the future.
They argue that:

"prevention is better than the cure, but only when it works".

What do you think?