Shares in Dobbies Garden Centres soared more than 17 per cent after the Scottish entrepreneur Sir Tom Hunter doubled his stake and said that he was considering launching a bid to rival that of Tesco.

The shares surge added £21.5 million to the horticultural specialist's market value and took it to £174.46 million — beyond Tesco's £155.6 million agreed offer price of last week.

Shares went to £17.85, up 260p. Tesco offered £15.00 a share.

Yesterday's Sir Tom's bid vehicle West Coast Capital said that it had almost doubled its stake to 20.6 per cent, close to the 25 per cent required to block a bid.

Today Sir Tom sold a 5.79 per cent stake in the recently floated Booker Group at 25p per share, collecting some £6.1 million for his 24 million shares which he owned through TBH Trading, a subsidiary of West Coast Capital. He sold in a placing alongside other investors.

West Coast yesterday said that it was "considering all its options in relation to its shareholding, one of which is a possible offer for the company".

Sir Tom Hunter already owns Wyevale Garden Centres and Blooms of Bressingham. Raising his stake buys him time to finance a Dobbies bid but could also flush out rival bidders such as private equity. Apax has previously been in talks with the company.

Richard Ratner at Seymour Pierce said: "We suspect that, rather than bidding and trying to take Tesco on in a straight fight, he [Sir Tom] is trying to frustrate Tesco getting to 75 per cent. It shows either how fearful his camp is of having another serious operator in this sub-sector, or that he is trying to get Tesco to raise its offer, which it might do to stop him getting to 25 per cent.

"On balance we think that the former is the reason, which leaves shareholders in an uncomfortable position if the bid fails."

Mr Ratner was telling clients "nervously" to hold their shares.

Tesco, which approached Dobbies to discuss a potential acquisition early last year, announced its agreement with the board after snapping up 22.6 per cent of shares and receiving irrevocable commitments from shareholders over a further 2.7 per cent.

Tesco's stake means it needs the backing of just over 52 per cent of Dobbies' other shareholders.

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