[Fruit & Veg]

I've got a client who would love for me to optimise his site using his competitor trademark terms and names. I've told him this isn't cricket and shouldn't be done plus he can do it to his hearts content on Google Adwords, but he now wants hard evidence of why this can't be done.

I've tried searching for hard evidence of the illegality or plain inhumanity of doing natural optimisation for competitor trademarks but have come up short. Can anyone point me in the right direction?

I've found a couple of US based cases but nothing in the UK.