Shares in ScottishPower have soared on the back of fresh speculation that a major European power firm has submitted a bid to acquire the UK utility.

The exact identity of the proposed suitor has not been revealed but reports have listed most of Europe’s big energy players, ironically with the noted exception of E.ON, as potential bidders.

E.ON would have been the obvious candidate as it attempted to buy the Scottish power company late last year. However, as the Dusseldorf-based firm is currently engaged in a drawn-out acquisition bid for Spanish power provider Endesa, current wisdom suggests that it is not the mystery bidder.

It has been speculated, however, that there could once again be German interest, with E.ON’s domestic rival RWE put forward by The Scotsman as a possible suitor. ScottishPower’s own compatriot Scottish & Southern Energy is another speculated interested party.

Meanwhile, reports have also mentioned Vattenfall, EDF, Enel and Gazprom (which has already revealed its keen interest in the UK energy market). However, according to The Independent newspaper, the undisclosed bidder is in fact Spanish outfit Iberdrola. The green energy champion is known to be keen to establish a pan-Euro presence and apparently has issued a GBP12 billion offer.

Whoever is the mystery bidder, news of the approach has aided ScottishPower’s share price, increasing it by around 60 pence following the news to 798 pence per share.