Scottish Power has agreed an £11.6 billion takeover by Spanish energy company Iberdrola.
The move comes three weeks after Iberdrola announced it was in talks about buying Scottish Power, which has more than five million UK customers.
Iberdrola, which employs 17,000 people worldwide and is a world leader in wind power, is the latest Spanish company to target a UK firm, following deals for O2, Abbey National and airports operator BAA.
If the takeover goes through, it will leave the UK with only two major quoted energy suppliers, Centrica and Scottish & Southern Energy.
The offer from Iberdrola may yet flush out other bidders, particularly as the price of 777p a share came in below market hopes for a figure of around 800p.
Scottish Power chief executive Philip Bowman, who led Allied Domecq before it was also taken over, said the deal enabled his company to expand its geographical and operational presence and diversify its portfolio.
He added: "This transaction achieves these objectives without the adverse social consequences for employees that would be likely in most other merger scenarios."
Mr Bowman said Scottish Power would now be better able to compete on a global scale and in an increasingly competitive environment.
