In a short notice today, the watchdog said it is considering whether the transaction “may be expected to result in a substantial lessening of competition” within the market.

The boards of both UK housebuilders agreed a merger deal in February, which priced Redrow at £2,524 million.

Under the terms of the deal to be put to shareholders, Barratt shareholders will get 67.2% of the combined group and Redrow shareholders will get 32.8%, effectively making it a Barratt takeover.

If approved, the combined group will be called Barratt Redrow and become a third brand and division of the group, alongside Barratt Homes and David Wilson Homes. The move would create a mega housebuilder turning over £7.45bn and delivering over 22,600 homes a year, based on past performance, with net cash of £874m.

The CMA has also today issued an “invitation to comment” to allow organisations to submit views on the proposed deal and how it may affect competition in the UK.

Subcontractors and suppliers with any observations on the merger can email the CMA by 2 April at Barratt.Redrow@cma.gov.uk.

The CMA already has another investigation ongoing into suspected breaches of competition law by the big eight house builders including Barratt and Redrow.