Shares in Scottish Power charged ahead after the energy giant revealed a forecast-beating set of first quarter figures.

Much of the improvement was attributed to a strengthened performance from Scottish Power's US business PacifiCorp.

The business was rocked by a temporary loss of output at its Hunter power station in Utah and blackouts in parts of California last year.

It lost out again after power prices collapsed and it was forced to take a charge against forward contracts agreed at higher prices.

Since then, Scottish Power has secured agreements with US regulators to raise customer bills to recoup some of the hefty losses incurred.

The group said PacifiCorp had enjoyed another quarter of improving financial performance in the last three months.

This was consistent with a goal of increasing operating profits in the next three years to about one billion US dollars (£636.9 million).

Operating profits in the quarter were £134 million at PacifiCorp, a 48 per cent rise following regulatory rate increases of £17 million and lower power costs.

It helped offset a weaker showing in the UK, which reported operating losses of £8 million against profits of £4 million in the previous year.

A spokeswoman attributed the losses to the traditionally weak time of year, which she said was still relevant even though the UK suffered from wet weather in the quarter and a fall in wholesale electricity prices.

Last year, Scottish Power had benefited from a stronger market for wholesale electricity.

Group profits were boosted by the sale of Worthing-based Southern Water earlier this year and a £27 million reduction in net interest charges to £69 million this quarter as a result of the deal.

Pre-tax profits came in at £152.1 million, up from £105.3 million, although Southern Water's removal from group sales also contributed to a fall in turnover, from £1.68 billion to £1.24 billion.