ScottishPower’s Spanish owner Iberdrola is planning to double its investment in Britain over the next five years, in an early win for the Labour government ahead of next week’s summit of international investors

Iberdrola will spend £24 billion on upgrading the high-voltage cables needed to transport power around the country and on building more wind farms.

About two-thirds will be spent on increasing the capacity of the electricity transmission and distribution lines that carry the clean power generated in Scotland to the south.

They will include a new subsea superhighway, Eastern Green Link 1, between Torness in Scotland and Hawthorn Pit in England.

About £4 billion will also be spent on the construction of two wind farms off the coast of East Anglia, which secured contracts in this year’s contracts-for-difference auction. East Anglia 2 and East Anglia 3 will generate enough power for about one million homes, Scottish Power has said.

The investment will help the UK meet electricity demand which is forecast to increase by 50% by 2035 as petrol and diesel cars are replaced with electric vehicles and households switch gas boilers for electric heat pumps.

In August, Iberdrola agreed to buy Electricity North West, the distribution network company covering the northwest of England, for about £2.1 billion.

Executive chairman Ignacio Galán calls its a “vote of confidence” in Britain, encouraged by greater regulatory stability and a “clear policy direction”. The commitment will make Britain its largest focus for investment.

More than a hundred international business leaders are due in London on Monday to attend the government’s first International Investment Summit.

Those committed include Eric Schmidt, the former chief executive of Google, Larry Fink, chief executive of BlackRock, and Yasir Al-Rumayyan, the governor of the Saudi Public Investment Fund. Ministers hope the summit will be used to announce deals worth tens of billions of pounds to the British economy.