A probe by the UK’s energy regulator has led shares in Moneysupermarket.com Group PLC (LON:MONY) and its rival Zoopla Property Group PLC (LON:ZPLA) becoming the worst performers in the FTSE All-Share index yesterday.

Moneysupermarket said: “Ofgem has opened an investigation into whether two or more companies providing a supporting service for the energy industry have breached competition law…Ofgem is gathering this information to establish whether to include the company as a subject of its investigation.” Ofgem had asked it for information as part of its investigation into “whether two or more companies providing a support service for the energy industry have breached competition law”.

Rival uSwitch, which has just been bought by online property website Zoopla in a deal worth up to £190 million, has received the same request.

Ofgem’s probe comes amid wider efforts by lawmakers and regulators’ to make the energy market more competitive and bring down prices. Price comparison websites such as Moneysupermarket and uSwitch have faced criticism recently for making it easier for consumers to switch to options that earn the companies a commission.

Moneysupermarket made the biggest drop on the on the mid-cap index, although Zoopla was not far behind, down 16p to 260p.

By Miranda Wadham