Centrica plc  (CPYYY) and other British energy stocks were left out in the cold Tuesday as investors responded to a pledge by the U.K. government to cap energy prices if it is re elected in June's general election.

Prime Minister Theresa May has said she will take as much as £100 ($129) off the annual energy bill paid by households in a clampdown on what the government has described as a "broken" market.

But critics have accused her of cynicism, given that the Conservatives attacked a similar pledge by the opposition during the 2015 general election campaign, while Centrica struck out at the plan during its annual shareholder meeting Monday.

Britain's largest provider of domestic energy, Centrica, told investors that May's policy could be counterproductive, as it might lead to less competition and higher prices in the long term.

May's promise has left investors fearing for both earnings and dividends across the sector, with British Gas owner Centrica seen as the most likely to reduce cash payouts to shareholders first, given its already low level of dividend cover.

Centrica stock led the sector lower Tuesday, falling nearly 4% to change hands at 194.6 pence, which brought year-to-date losses for shareholders to 16.7%.

After stripping out one off gains during the recent fiscal year, Centrica had earnings per share of just 16.8 pence, which is expected to rise only modestly to 17.0 pence during the current year.

But total dividends in the year to Dec.31 2016 were 12.0 pence per share, unchanged from the year before, which left dividend cover sat at a paltry 1.4 times.

The company cut its dividend at the beginning of 2015 and again at the beginning of 2016, as it grappled with the collapse in energy prices, and so it has form for axing shareholder returns when the going gets tough.

The company said in Monday's trading update that warmer weather has meant lower demand for household energy during the winter months, while wholesale prices were also lower.

Other energy stocks, such as SSE (SSEZY) and National Grid (NGG) were all lower, by 1.5% and 0.5% respectively in early trading.

National Grid's dividend cover also came in at 1.4 times for the recent full year although, as an infrastructure provider and not an energy provider, it is seen as less exposed to the price cap.

It also has greater diversification, both internationally, as well as across gas and electricity. A pledge to grow the dividend in line with inflation might also be helping to prop up the shares.

SSE also has more diversification across retail, commercial and wholesale supply markets, although its dividend cover was the lowest of all three companies, at just 1.3 times, for the recent fiscal year.