ENERGY giant ScottishPower’s owner has revealed that earnings from its UK generation and supply have dropped by more than three-quarters (76 per cent) after it lost around 100,000 customers in the first half of the year.

ScottishPower saw customer numbers drop to 5.3 million in the first six months of 2017, down from 5.4 million over the same period last year.

The company had raised dual-fuel prices by 7.8 per cent in March, but said its numbers were stable.

“We have still retained more of our customers over the last five years than any other large supplier,” said Keith Anderson, ScottishPower’s chief corporate officer.

Its Spanish parent company Iberdrola said the UK supply unit had also been hit by milder weather conditions and the closure of the Longannet power station in Fife.

It said domestic power sales were down by about seven per cent and domestic gas sales dropped by around eight per cent.

This caused earnings in UK supply generation and supply unit to come in at £48.8 million for the period, down from £205.9m for the first half of 2016.

Anderson said: “In retail, we have seen fierce competition in the UK and we expect this to continue for the foreseeable future.”

Iberdrola’s group revenues for the half year rose 1.8 per cent to €15.2 billion (£13.5bn), while gross margin increased by 1.1 per cent to €6.9bn (£6.1bn).

Net profit climbed 4.2 per cent over the period to €1.5bn (£1.3bn).

ScottishPower Renewables, the Big Six provider’s green energy operation, bolstered its onshore wind production by 43.8 per cent to 1,701 GWh for the half year thanks to better wind conditions.

Anderson added: “Investment continues at pace in major infrastructure.

“We are nearing the completion of a £650 million programme to deliver eight new onshore windfarms and we are starting full construction of the £2.5bn East Anglia ONE offshore windfarm. As part of our 2016 to 2020 business plan, ScottishPower is overseeing around £4m of investment every day.”

In April, Anderson hit out over Government plans for a price cap on gas and electricity bills, warning it could harm competition.

He said the Government should instead make the “bold move” to scrap standard variable tariffs (SVTs) and only use price caps as punishment for firms that failed to move customers on to better value fixed deals.

While the Tories promised a wider price cap that would benefit 17m customers before the General Election, the policy did not appear in the Queen’s speech following Theresa May’s failure to win a majority.

Separately, around 230,000 households deserted another Scotland-based supplier SSE in the three months to the end of June – taking to a third of a million the total customers both companies have lost.

SSE, the UK’s second-biggest supplier, raised its dual-fuel prices by 6.9 per cent in April.

Its figures show an acceleration of customers leaving — after losing 210,000 in the whole of the previous year. It blamed a “highly competitive market”.

Both sets of figures continue the trend that has seen households leaving the Big Six suppliers, and moving to smaller – so-called “challenger” – companies. More than 50 suppliers are now offering electricity and gas to households across the UK.

Five of the top six suppliers have increased prices this year - with the exception of British Gas, which promised to freeze prices until August. The biggest increase came from Npower, which announced a 9.8 per cent rise in its dual-fuel tariff in March.