Thomson Financial, the data provider, has rejected Citigroup's claim for a credit on oil company Norsk Hydro's $28bn (€21.3bn) takeover by Statoil, leaving Morgan Stanley in line to clinch Europe's M&A crown.

Thomson said in a statement that "after extensive dialogue between all parties, [it] has decided not to list Citigroup as an adviser to the Norsk/Statoil transaction".