Multiple domain names to one site

One of our websites currently has 3 domain names pointing at it (there is only one set of pages the domains all point to the same space) The client who owns the site has hired some VERY expensive SEO advisers who have come back to us and said we have to put ASP (i guess they might mean 301??) redirects on each domain so as to avoid google's duplicate content filter. I can't what the benefit is of adding pages with redirects over the current system.
Can anyone tell me if this is better? Can google not see through both systems? Thanks for any advice!

What you need is to keep your main domain as it is, and re-direct the entire lot of the other two domains using a 301 (can be ding in ASP, PHP, htaccess, Apache, or any other server-side language).

When you do that, Google and other SE's will see them as all being directed to the main site, so you'll get the best benifit from it.

As far as adding pages with re-directs, that is useless. Just got to add those pages to the main site, not the other domains.

Hi, thanks Catacaustic, I'll get onto that!