Glencore, the publicity-averse trading house renowned for its far-reaching influence on global commodity markets, is exploring a stock market flotation.

Switzerland-based Glencore, one of the world's largest private companies, has held preliminary talks with bankers about an initial public offering as it reviews its partnership structure.

While an IPO is not considered imminent, a move into the public spotlight would mark a big change for the company founded in 1974 by Marc Rich, a one-time fugitive financier who was famously pardoned by Bill Clinton during the former US president's last day in office.

However, the financial constraints imposed by its private structure are now seen by some near the company, which Mr Rich sold to former associates including current management in 1993, as inefficient and a barrier to growth.

While its private status has given Glencore flexibility to pursue opportunities more quickly than if it had been a public company, the liabilities of its low-profile approach have also become apparent.

Over three months from September 2008, the cost of insuring Glencore against a default on its debt spiked 16-fold to more than 3,000 basis points, on market speculation over its liquidity.

This was a “wake-up call”, one person familiar with the company said, as management realised the reputational damage that can hit companies without the degree of public disclosure that quells rumours.

Even though rating agencies describe Glencore's liquidity as healthy, one of the main reasons for a flotation also seems to be finding new sources of expansion capital.

Some 60 per cent of profits are retained in a scheme to fund pay-outs to partners who leave the group, according to a report on Glencore by Standard & Poor's, the credit rating agency.

Bankers have courted the company for years but only in the past year has Glencore become open-minded to schemes to raise “permanent capital”.

“It is all about finding the right time,” said one banker. Glencore's interest in an IPO was firm but preliminary, he said, adding it was more likely in the medium term when commodities prices improved.

As much of Glencore's $14.4bn in net debt is held in bonds, it discloses quarterly financial information to bond holders.

It lifted revenues last year from $142bn to $152bn, according to S&P. Underlying profits – earnings before interest, tax, depreciation and amortisation – fell from $5.5bn to $4.4bn during the year.

Glencore also has extensive direct interests in mining companies including a 35 per cent of the London-listed Xstrata. Glencore declined to comment.