Gurantor and rental increase

Hi,

I'm just wondering if guarantors are required to be made aware of rental increases during the term (and extension) of the tenancy agreement?

The original tenancy agreement was for one year and has since rolled over into several years. The document that the guarantor signed makes explicit reference to any extensions and how that would not affect their agreed liability. The document (and subsequent google searches) does not make it clear whether the rental increase results in their release of guarantor responsibilities or not.

Any help is gratefully received, thanks.