The control of India's largest brewer hangs in the balance after the agreed £7.8 billion bid for Scottish & Newcastle (S&N) by Carlsberg and Heineken.

United Breweries (UB), which accounts for about half of Indian beer sales and is best known as the maker of Kingfisher, is 37.49 per cent owned by S&N and the British group's Indian operations will be taken over by Heineken once the deal is completed.

However, Indian regulators gave warning that a change in ownership of the stake could trigger an obligatory open offer for the remainder of UB.

A source at the Securities and Exchange Board of India said that the financial watchdog could force an open offer as a stake of more than 15 per cent of UB was about to change hands, although bankers in Bombay said that a cross-border takeover under a scheme of arrangement could sidestep the requirement for an open offer.

Vijay Mallya, the chairman of UB, would be likely to resist fiercely any loss of control in the group, in which he holds a 37.49 per cent stake.

Mr Mallya was the driving force in the rise of UB to become one of the world's three largest spirits producers and under his agreement with S&N the British company had a limited say over UB's strategy.

Analysts said that Heineken, which has identified the potential for growth in India's booming beer and spirits market, could prove to be a far more proactive partner. A spokeswoman for Heineken said that it was too early to elaborate on the Dutch brewer's plans for India. “All we will say is that India represents a great opportunity,” she said.

Sources close to the S&N takeover, which is in the offer period, suggested that talks were ongoing over the fate of UB. “We are trying to make this bid fly and are dealing with some very sensitive relationships,” one source said.

S&N has said that the fate of its stake in UB would be revealed only when the final scheme of arrangement governing the takeover was presented to shareholders next month.

Mr Mallya issued a guarded welcome to the prospect of a partnership with Heineken. “While the UB Group has had an excellent and productive relationship with S&N, we welcome the fact that Heineken will be associated and be a potential shareholder on terms that are yet to be discussed and agreed,” he said in a statement.

In the Indian press Mr Mallya, whose fortune is estimated at about £750 million, has suggested that he had the first right of refusal over S&N's stake in UB, but he has not identified the conditions under which such an option could be activated.

Analysts suggested that Mr Mallya's ability to increase his UB holding was limited after a run of acquisitions. In May last year he bought Whyte & Mackay, the whisky label, for £595 million and he owns Bouvet-Ladubay, the French winemaker, and a stake in Deccan Aviation, an Indian airline.

There has been speculation that Heineken could offload the UB holding to another brewer, with Anheuser-Busch, the maker of Budweiser, the Belgium brewer InBev and SABMiller named as potential buyers.

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