The Competition and Markets Authority said that its initial review of the proposed deal raised competition concerns in the supply of ready-mixed concrete in the Cardiff, Bridgend and Carnforth areas, where both companies are close rivals.
It warned that the lack of other strong suppliers of ready-mixed in these areas could mean that customers would face increased prices or a worse quality of service as a result of the proposed merger.
At the same time it cleared Breedon’s plans to acquire four quarries and an asphalt plant from Tarmac.
Tarmac now has until 3 May to address the concerns to prevent the merger being referred for an in-depth investigation by an independent group of CMA panel members.
Quarries being exchanged are located in Scotland, Cumbria and North Wales, together with a quarry and asphalt plant in West Wales.
Ready-mixed concrete operations being offloaded from Breedon’s network of 200 plants are in multiple locations extending from Dumfries in Scotland to Exeter in Devon.
Daviot Quarry, Inverness
Low Plains Quarry, Penrith
Borras Quarry, Wrexham
Minffordd Quarry & Asphalt Plant, near Porthmadog
Breedon ready-mixed concrete plants
Briton Ferry Portsmouth
Dunald Mill Tredegar