Is exclusion of liability for injury caused by negligence lawful?

I refer to the letter "Indemnity forms unfair to participants" by Mr David Kwok Ng Kan (Nov 1).
Given the prevalence of this practice in the workplace and educational institutions,
perhaps it should be made a criminal offence
for anyone to purport to exclude liability in such circumstances.
Peter Wadeley
http://www.todayonline.com/Voices/EDC101103-0000045/Is-exclusion-of-liability-for-injury-caused-by-negligence-lawful?

My view
I agree that it is unlawful for a party to exclude liability in circumstances where they were negligent. The exclusion is unfair to consumers and goes against the established law of negligence.

Instead of waiting for Parliament to pass a new law, the relevant authority has existing power to tell these parties that they are doing something that is illegal. The relevant authority should step forward and exercise the powers that they already have, instead of standing by and watch.