Spanish regulators have approved the surprise 26.9bn-euro ($34bn; £18bn) takeover of power firm Endesa by German rival E.ON despite government concerns.
Energy takeovers are as much about politics as they are business
The move proved controversial and came after Spain's government had already given its blessing to a bid for Endesa from Spanish energy group Gas Natural.
Energy is a hot political topic after prices surged and many nations are keen to create large national providers.
While giving the go-ahead, regulators attached 19 conditions to the E.ON bid.
The German company said it remained committed to the deal, but did not see the need for the regulator's caveats. Press reports suggested that E.ON could be mulling legal action in an effort to challenge the conditions of the ruling.
The European Union said it had yet to see the terms of the approval and declined to comment further. Brussels has already told Spain not to use its veto to block the takeover.
Under the terms of the approval, the Spanish regulators want E.ON to keep Endesa separate from its other operations, limit the firm's debt levels and keep up its current, and planned, levels of investments.
The German firm also will have to sell some of Endesa's domestic businesses, including its one-third share of the Asco-1 atomic reactor.
E.ON will also have to sell coal-fired generating power plants and commit to keeping gas supplies at previously agreed levels.
Analysts said that while the conditions were harsh, they were in line with what the market expected. E.ON's shares were down 0.5% in Frankfurt, while Endesa's rose by almost 2% in Madrid.
Votes or profits?
The question of who controls national power supplies is becoming an increasingly fraught subject, and has often pitted free-market ideals against national economic interests.
Many Europeans are facing hikes in their gas and electricity bills, and governments are acutely aware that shortfalls in local energy provision could leave them vulnerable to the whims of supplier nations.
As a result, there has been a renewed focus on the viability of nuclear power and renewable energy sources such as solar, wave and wind power.
The UK, for example, recently unveiled a review of its energy strategy that said Britain needed a fundamental rethink.
At the same time, companies are looking to access markets such as Spain with their increasingly power-hungry consumers, and merge national operations in an effort to cut costs and become pan-European power providers.