Spanish utility Iberdrola is to pump a further $8bn (£4bn) into US renewable energy resources over the next two years.

The investment was unveiled by Iberdrola president Ignacio Galán in a speech at the XIII Forum of the US/Spain Council in Houston.

But the investment will go ahead only if the US improves its regulatory framework, “which must be predictable, sufficient and provide stability”, warned Galan.

Most of the investment will be in wind power, into which the company has already ploughed $900bn in the US to become the second largest operator by capacity in North America with an installed capacity of 2,400Mw. The new investment would double this capacity.

Galan told his audience in Houston that he is gambling on 15 per cent growth in the North American wind market, and that reforms of the US energy regulations – especially of the administrative process involved in the construction of the new electricity networks – would continue apace.

Other large investments in wind power – especially in Texas – have been reported recently.

Spain led Europe in new wind installations in 2007, according to a recent Wordwatch’s study, and now ranks third worldwide in total wind capacity with 15,145Mw. Iberdrola has a global installed wind power capacity of 8.200Mw in 22 countries.

Iberdrola, along with EDF, E-on and Centrica, is one of the companies linked to the sale of British Energy which runs Britain’s nuclear plants.