The Authority claims the deal would reduce competition in the Irish insulation materials market.

It follows a four-month investigation and is only the second time a merger has been blocked since January 2003, when the Act regarding merger control came into force.

The Authority said: “We have decided to block the acquisition on the grounds that such a transaction would substantially lessen competition in the manufacture and provision of insulation materials in the state.”

The Hytherm/Xtratherm Group, which is based in Ireland and the UK, manufactures a range of rigid insulation boards. The Xtratherm range of closed cell rigid foam insulation includes XT/TH for use between studs or as an insulated lining in timber frame constructions.

The Authority’s decision means the acquisition may now not go ahead.