It is understood that the firm was this morning set to announce a 3.3 per cent drop in charges, a £42 reduction on the average annual bill.
It is thought that ScottishPower will also promise to pass on a further £12 rebate to all customers for the warm home discount, which the government has said will be funded through general taxation instead of through levies on energy bills.
Labour last week called on ScottishPower and rivals npower and SSE to immediately reduce prices for households after the government last month slashed green levies.
Caroline Flint, the shadow energy secretary, said it was a “scandal” that three of the “big six” providers had still failed to pass on the savings a month after the green levy reductions.British Gas has already reduced prices in response, announcing in early December that it would reduce bills by 3.2 per cent on New Year’s Day, scaling back hikes that saw prices go up by 10.4 per cent for electricity and 8.4 per cent for gas in November.
EDF and E.ON took the levy changes into account in the recent round of price rises, increasing tariffs on average by 3.9 per cent and 3.7 per cent respectively – far less than the increases announced by rivals.
SSE and npower are expected to follow ScottishPower by passing on levy savings.