The UK's Office of Fair Trading may fine the global drinks company Bacardi-Martini up to £40m for an alledged breach of UK competition rules.

In what it calls a "proposed decision", the OFT wrote to Bacardi this weekend saying why, by entering into a number of agreements requiring pubs and bars to sell only white rum produced by Bacardi, the company had breached fair trading rules. 

The "exclusivity" deals that Bacardi is accused of arranging with pubs and bars have been under investigation for a year by the OFT. And they could result in the rum maker being fined a maximum of 10% of it annual UK turnover of £400m.

The largest fine imposed by the OFT so far is £2.2m.

Bacardi now has the opportunity to make written and oral representations in response to the OFT's proposed decision. These will be taken fully into account before any final decision is made.

A spokesman for the OFT said: "Because this is a proposed decision we can't go into any more detail." But insiders said its document is 100 pages long.

Bacardi Martini has said it disputed the OFT's findings.

A spokesman said: "Bacardi Martini UK is disappointed to have received the OFT's notice. The company has fully co-operated with the OFT throughout its initial investigation and will continue to do so.

"However, Bacardi Martini is prepared to vigorously defend its position and will be considering its response in due course."