The future of one of Scotland's last complete whisky companies, Whyte & Mackay, will be decided in the next few days by the Office of Fair Trading.

The regulator is expected to pronounce imminently on whether Scotch whisky giant Diageo will be able to hang onto W & M, which it acquired as part of its £344 million deal earlier this year to take a controlling 25% interest in India's United Spirits, the creation of tycoon Vijay Mallya.

According to Indian reports, United Spirits has anticipated the verdict and begun to scout out possible buyers for the business, which it values at $1.5 billion (£900m).

A senior United official has told the Indian press: "The intention is to retain Whyte & Mackay. It is a valuable asset for us, and with the value of Scotch growing in global markets, this asset is strategic in nature."

He said the OFT's verdict was finely balanced, and that one outcome might be the phased reduction of control over the asset over a period of time.

The OFT signalled its concern in July by issuing an "invitation to comment" on whether the deal signed between the Johnnie Walker owner and Mr Mallya would have a detrimental impact on the spirits market.

Whyte & Mackay is an integrated producer with its own blended brand, a grain distillery at Invergordon, bottling plant at Grangemouth, and malt brands including Jura and Dalmore, while Diageo is the world's biggest whisky producer. In a major report on its activities, published earlier this week for the first investor briefing by new chief executive Ivan Menezes, Diageo revealed that it has a total market share of 35% worldwide, including 44% of the standard Scotch category, 50% of premium and 44% of super-premium.

Alan Gray at Sutherland's in Edinburgh, author of the Scotch Whisky Review, said Diageo did not need the W & M assets, but might like to hang onto the grain distillery and possibly the malt brands, particularly Dalmore - but he doubted it would be allowed. "It is quite attractive because there are very few companies like that any longer, so much rationalisation has taken place. A clean sale would be the best thing, certainly from the point of view of jobs it would be the ideal solution."

Mr Mallya paid £595m for W & M in 2007, and its current value is being touted as £900m. Mr Gray said that sounded "a bit rich" but it would depend on whether the group had been building up its stocks, which had been appreciating in value. He said any sale would bring out potential buyers in India, Russia and China as well as Diageo rivals such as Bacardi and Brown Forman, and private equity interest, for a relatively rare opportunity. "It is about how much somebody wants it and what they are willing to pay."

The OFT could ask the companies to agree to sell certain brands or businesses.

An industry observer in Scotland commented: "Whyte & Mackay is important in Scotland but it is only a small part of the United acquisition, which was all about Diageo securing important routes to market in India for brands they have already got."

A Diageo spokesman said: "We are aware that the OFT are due to say something but we have no idea what."