Nov 24 (Reuters) - Britain's competition regulator said on Friday the proposed acquisition of demolition waste recycler Mick George Ltd (MGL) by Heidelberg-owned building materials firm Hanson could result in less choice and higher prices for building contractors.

The Competition and Markets Authority (CMA) after its Phase 1 probe said the proposed deal raised competition concerns in 18 markets for two key building materials in the East of England and the East Midlands.

The CMA started its initial phase of investigation of the proposed acquisition in September after the companies announced the deal last December.

The regulator said both Hanson and MGL supply aggregates, used in the construction of roads and buildings, and ready-mixed concrete.

Hanson and MGL now have five working days to address CMA's concerns.

(Reporting by Aby Jose Koilparambil in Bengaluru; Editing by Nivedita Bhattacharjee and Dhanya Ann Thoppil)