Any customer signing up to the new tariff will be given the option in 12 months' time to extend their deal until January 31st 2011.
Gerard Magee, head of marketing at ScottishPower, said the new scheme was part of the firm's "long-term strategy to offer price savings where possible".
"By launching PriceSure, our new fixed-price product, customers will have an opportunity to make savings of up to 10 per cent on current standard gas prices," he added.
"In terms of our general prices, we are still monitoring the wholesale markets very closely. If we continue to see a sustained drop in wholesale energy costs then we will reduce prices as soon as we're able."
ScottishPower recently launched a new social tariff for its most vulnerable customers, which offered annual savings of £211.
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