German energy giant Eon has warned the Conservative Party's proposed price cap on standard energy tariffs could "really ruin things" for its business in the UK amid warnings investors could be put off should the policy become law.

The €16bn parent of Eon UK - which has approximately 4.6m customers in the UK - is the latest energy company to insist that rising competition in the UK energy market could be dashed by “excessive regulation” of energy prices.

Britain’s two largest energy suppliers - British Gas and SSE - have already spoken out against the Tory’s plans to intervene in a bid to ‘fix’ the market after a rash of price hikes earlier this year.

The market value of Centrica, the owner of British Gas, dropped by almost 5pc to lows of £1.92 a share following the publication of the Tories’ price pledge. Meanwhile SSE slipped by over 3pc to just over £14.