The regulator is inviting comments on the proposed deal from any interested party by 6 November and plans to make a decision by 18 December

The CMA is considering whether the transaction would result in the creation of a relevant merger situation under the merger provisions of the Enterprise Act 2002.

If the acquisition does result in a merger situation, the CMA will look at whether it might result in a “substantial lessening of competition” within the UK energy market.

Ovo announced its plans to buy SSE’s household energy business last month. The £500m deal will see Ovo acquire SSE’s household energy and related services business in the UK, which includes the customers, operations and employees for energy, telecoms and home services.

If it goes ahead, the move would propel Ovo into the “big six” energy suppliers alongside British Gas, nPower, EDF Energy, Scottish Power and E.ON.

SSE previously had plans to merge with nPower last year but the deal was scrapped after the companies failed to reach an agreement on financial contributions to support the combined entity.