Napier is teaming up with Cinven, which recently sold IPC Media to AOL Time Warner, and CVC Capital Partners.
They join other bidders, which are believed to include Carlsberg Tetley, the UK arm of Danish brewer Carlsberg, and rival Danish brewer Heineken. US beer giants Coors and Molson have also been linked to bids.
The price for the business is likely to be high, with estimates ranging from between £1bn to £1.3bn.
Interbrew announced in September that it would sell the premium UK beer brand as part of a compromise deal worked out with the UK competition authorities, following its takeover of Bass Brewers.
To comply with UK competition rules, a brewer can not control more than 30% of the market. Carling alone has a market share of 18%, while Carlsberg Tetley has 12%.
The UK secretary of state Patricia Hewitt ordered Interbrew to sell either Carling or Bass Brewers so that it would remain inside competition regulations.
If Carlsberg does bid for the brand, it could find itself up against strong opposition from another Danish player Heineken, which is keen to pick up Carling to sit alongside its own Heineken brand in competing against Interbrew's Stella Artois.
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