The UK’s Office of Fair Trading may take up to six months to review its interim ruling that has prevented the London Metal Exchange from extending electronic trading hours, an OFT spokeswoman said on Tuesday.

The OFT is investigating whether the planned six hour extension in trading hours of the LME-Select trading system will contravene European Union competition law. Its interim ruling this week followed a complaint by Spectron Group, which has a competing electronic system for clients to trade copper, aluminium, nickel and zinc.