Investors in the two largest UK-listed energy businesses are wrapped in a financial duvet this winter. While the share prices in Centrica and SSE may have dipped last week on the back of Ed Miliband’s threat of a price freeze, they are well ahead of their 2009 level. Centrica’s share price is up by more than half at 367p. SSE stood at £10.60 in early 2009 and closed at £14.74 on Monday.

Then there are the ever-rising dividends. Without any interruption for the financial crash, SSE’s shareholder payout has climbed from 26.4p a share in 2004 to 56.1p last year.

On Monday SSE pledged to maintain its generous payout despite predicting that first-half profits would be lower than analysts’ expectations. How can it insulate investors in this way? We only need to look back to May when it warned consumers to brace themselves for further price rises.

No wonder Miliband blasted the industry. Until now it has proved immune to criticism that it siphons consumer cash and deposits it in the bank accounts of investors.

Even SSE’s defence that it will maintain a £1.5bn investment programme rings hollow when the risks attached to that investment are near zero. It plans to build wind farms near its Scottish base with a guarantee from the government of a premium rate for the electricity.

Then there is the upgrade of the grid. The regulator insists on a five-year programme. This is the only real cost for inheriting the infrastructure at a knockdown cost.

Yet investors should be wary. They could be left exposed like the shareholders in EDF, RWE and E.ON who have suffered 80% share price falls since 2008 following tough government action in their home markets for France and Germany. A future British government may follow suit.