Subject to the provisions of this section, the proportion, if any, of the aggregate amount of the housing support grants payable for any year to a local authority shall be determined by the Secretary of State, after consulting with such associations of local authorities as appear to him to be concerned, by such method as may be prescribed.

A prescribed portion of the aggregate amount may be apportioned to a particular local authority.

In prescribing the method of determining the proportion, if any, of the aggregate amount of the housing support grants payable to a local authority for any year, the Secretary of State may take into account any substantial difference in the actual amount of any element of their eligible expenditure as compared with any estimate of the amount of that element made by him in determining the proportion payable to them for a previous year.

In prescribing the method of determining the proportion mentioned in subsection (1) payable for any year to a local authority the Secretary of State shall have regard to any special needs affecting eligible expenditure.

The Secretary of State may, for any year (in this subsection referred to as "the current year"), prescribe such method of determining that proportion as to secure that no reduction in the amount of housing support grant payable to any local authority for the current year as compared with the amount of housing support grant so payable for the immediately preceding year is so great that there is an unreasonable increase for the current year over that preceding year in the amount of the authority's eligible expenditure which is required to be met by way of rent or rate fund contributions.

In this section "prescribed" means prescribed by a housing support grant order.