Northern has had several offers of support from investment banks, which are now talking to possible suitors in the US, France and Britain.
The favourite candidate to emmerge as a white knight is Houston Industries, which held tentative talks with Northern earlier in the year and is known to be interested in establishing a presence in the UK electricity industry. Florida Light and Power and Pacific Gas and Electric are also touted as possible bidders from the US.
A bid from a domestic energy company is unlikely in the light of recent government rulings to block intra-industry mergers. An approach from a water company is possible.
Lyonnaise des Eaux, which owns Northumbrian Water, could be interested in creating a north-eastern water and electricity combination.
Severn Trent, which had its bid for South West Water blocked last month by Ian Lang, President of the Board of Trade, is looking for investment opportunities.
Michael Cohen at Salomon Brothers said: "It has been our opinion that Severn Trent would be better off using its cash to purchase a REC than participating in a competing bid for South West Water. There is a more promising future for companies as multi-utilities rather than remaining a one-utility service provider."