GlaxoSmithKline Plc has resumed the hunt for a buyer for the European slice of its non-core drugs portfolio, with buyout firms and rival drug companies in the running to cherry pick consumer health brands, people with knowledge of the process said.

Among the groups circling the assets, buyout firm Bain Capital has teamed up with Belgian over-the-counter (OTC) drugs group Omega Pharma and Dutch private equity group Waterland to pursue a bid, people familiar with the process said.

Bids for the European portfolio are due on Wednesday, with rival pharma groups including Sanofi and private equity firms including Advent International and Avista, expected to be eyeing all, or just parts of the portfolio, some of the people said.

Britain's biggest drugmaker sold a range non-prescription products in North America to Prestige Brands Holdings
for 426 million pounds in December, after failing to find a single global buyer.

That leaves a collection of painkillers, dietary supplements, stomach and other treatments up for sale in Europe, which people involved in the process said might fetch up to 500 million pounds.

GSK and potential bidders declined to comment or were not immediately comment.

GSK has also yet to dispose of global rights to Alli, its over-the-counter (OTC) weight-loss drug, which has been the subject of health concerns, and could be sold separately, people said.

By teaming up with an established OTC player in Omega, whose brands include Buttercup cough syrup and wart and verruca treatment Wartner, Bain will be hoping it stands a better chance of securing a deal this time around.

The Boston-based private equity firm was pipped by Prestige in the final stages of an arduous auction process that ran for much of 2011.

Omega Pharma bills itself as an OTC pharma specialist and is controlled by chief executive Marc Coucke, who bought out the Brussels-listed group last year with the financial support of Waterland.

GSK first announced in February 2011 that it planned to dispose of non-core brands sold primarily in North America and Europe and representing about 10 percent of its consumer health portfolio, in order to focus on priority brands and emerging markets.

Cash from the sale, run by Goldman Sachs , is to be returned to shareholders.

Analysts initially said all the OTC products together might raise between 1.5 billion and 2 billion pounds, or three to four times annual sales. But expectations have come down since then.

Bankers said some buyers eyeing the European business were put off by the fragmented and small-scale of some of the brands in certain markets.

(Additional reporting by Ben Hirschler in London and Phil Blenkinsop in Brussels; Editing by Will Waterman)