Ineos, the chemicals business that is Britain’s biggest private company, and the UK polymer operations of Norsk Hydro have been raided by European Commission inspectors in connection with Ineos’s planned takeover of the Norwegian group’s British operation.

The raids on several offices in the UK on Tuesday came after concerns that a merger was going ahead without official approval from the Commission. Ineos, which has been built up from some of the devolved businesses of ICI, is buying Norsk Hydro’s polymers division for 5.5 billion crowns (£496 million). However, the European Commission is not due to approve the deal until February 18. The two sides have previously said that they expected to complete the deal in the first quarter of next year.

Norsk Hydro said that its factory in Newton Aycliffe, County Durham had been raided, and Ineos, which is head-quartered in Hythe, Kent, confirmed that it had been visited by inspectors but would not say which sites had been affected.

A spokesman for the Commission said that merger regulations prohibited a takeover from being implemented before it received official approval. He said: “The inquiry is also aimed at establishing whether there may have been an exchange of information between the companies in possible breach of EC treaty rules outlawing cartels and restricted business practices.” Both companies said that they would cooperate with the investigation and that they believed that they had complied with the regulations. The deal between Ineos and Norsk is the latest stage in the rapid rise of the chemicals business.

Ineos was launched nine years ago by Jim Ratcliffe, an engineer-turned-investor. In 2005 he bought Innovene, BP’s chemicals arm, for £5.1 billion in a deal that quadrupled Ineos’s revenues. Mr Ratcliffe has since embarked on a steady spree of buying up chemicals operations, many of which were offloaded by ICI as the former UK industrial bellwether reshaped itself.

Ineos’s acquisition of Norsk Hydro’s polymers business had raised some concern in the chemicals industry about Ineos’s subsequent strong market position in suspension PVC materials. “The European Commission can confirm that it undertook an unannounced inspection in the UK,” Jonathan Todd, spokesman for the EU’s competition regulator, said. He said that Article 7 of the merger regulation prohibited mergers from being implemented before they received approval.

“The inquiry is also aimed at establishing whether there may have been an exchange of information between the companies in possible breach of EC treaty rules outlawing cartels and restricted business practices,” Mr Todd said. He would not say whether it expected to announce the results of the raids before the planned decision on the takeover in February.

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