No 3 global broker Willis has had its “informal” offer for No 1 broker Marsh & McLennan rebuffed, according to London media reports.

Willis Chairman and CEO Joe Plumeri has made no secret of his ambition to lift his company into the top two and has reportedly lined up private equity company Kohlberg Kravis Roberts (KKR) to finance the bid.

A Willis spokesman in London has dismissed the reports as conjecture, but there’s some logic behind the speculation. KKR took Willis private in 1998 in a $US1.7 billion ($2.27 billion) management buyout and hired former Citigroup Vice President Mr Plumeri as CEO.

Willis was floated in 2001 and now has a market capitalisation of about $US5.6 billion ($7.46 billion).

A successful bid for Marsh would create a company valued about $US21 billion ($28 billion). Willis is said to be offering a cash and shares deal, with KKR financing the cash element.