I came across the following page from the UK government's website:
For a periodic tenancy (rolling on a week-by-week or month-by-month basis) your landlord can’t normally increase the rent more than once a year without your agreement.
For a fixed-term tenancy (running for a set period) your landlord can only increase the rent if you agree. If you don’t agree, the rent can only be increased when the fixed term ends.
I've tried in vain to find the law behind this, but I can't seem to figure it out. The page makes no references to actual law. Why can a landlord "not normally increase the rent more than once a year"? What would be illegal about writing an AST agreement that allowed the landlord to increase the rent every month after the fixed term period?
Also, it says that the landlord can increase the rent "when the fixed term ends". Does this also apply to an AST agreement where, when the fixed term ends, the agreement switches over to a month-by-month rolling basis? For example, say that the tenant signs an agreement with the landlord for a 6 month AST. At the end of the 6 months, the tenant continues to live at the property - can the landlord now increase the rent, as the fixed term is over? Thereafter, how often can they increase the rent? If it's once every 12 months, is it 12 months from the beginning of the agreement or 12 months from that first rent increase after 6 months?
Again, a pointer to the law on this would be helpful.