Sir Tom Hunter, Scotland's richest man, is going to court to try to stop supermarket behemoth Tesco diluting his power at Dobbies Garden Centres.

The billionaire Ayrshire entrepreneur yesterday said he had filed an application for a court order to block a proposed Dobbies rights issue that could end up costing him £44m to keep his near-30% stake in the company.

The legal action, which is the latest twist in the protracted tit-for-tat war between Hunter and the retail giant, has been raised in response to Dobbies' planned £150m fundraising - underwritten by 65% shareholder Tesco - that will double the number of Dobbies shares in issue.

Last August, Tesco, which is the UK's largest retailer, announced it had won enough shareholder support to make its £156.6m offer for Dobbies Garden Centres unconditional, thus thwarting Hunter's attempts to scupper the deal.

Hunter, who already owns Wyevale Garden Centres and Blooms of Bressingham, made no secret of the fact he believed the Tesco bid undervalued the business.

However, last month, the Dalkeith-based garden centre empire said that it wanted to issue up to 12.45 million shares at 1200p each in an open offer on a six-for-five basis.

The rights issue, which still has to be approved at a shareholders meeting in Dalkeith on May 27, has been widely regarded as an effort by Tesco to tighten its grip on Dobbies.

Nonetheless, Dobbies chief executive James Barnes yesterday insisted the move was aimed at raising money to fund the group's expansion plans and to pay down debts.

With summer fast approaching, the gardening sector is seen as fast-expanding and reasonably immune to an economic slowdown.

Dobbies, with a chain of 24 stores across Scotland and England, is an exception in an otherwise highly-fragmented market.

Beyond Hunter's 29.5% stake - which is held through his West Coast Capital investment vehicle - and Tesco's 65% shareholding, the remainder is owned by about 300 small investors.

If the issue proceeds, Hunter will need to stump up £44m to retain his stake. If none of the minority shareholders participates, Tesco's holding could rise to 83%.

A spokesman for Hunter yesterday told The Herald: "We don't believe this is in the interests of all shareholders. It's a good deal for one shareholder and one shareholder only - Tesco.

"We look forward to the judgment on Monday."

Tesco is understood to be keen to chase the green pound and use the stores to offer consumers ecologically-friendly power solutions, such as wind turbines or solar panels for their homes.

Asked to respond to the claim that the rights issue had been designed to make life difficult for Hunter and the entrepreneur's legal challenge, Barnes said: "Obviously, we are a little disappointed.

"From our point of view, well, we need the money. We are now at 220% gearing and more than £100m of debt. We also plan to use the money for expansion. The money will be earnings-enhancing from day one - so that's good for all shareholders."

Regarding Monday's court hearing, Barnes said: "My understanding is that both sides will put their case forward and the judge will decide whether or not there is a case to be answered."

Nonetheless, at the same time, Hunter has appeared determined to remain a thorn in the side of the giant.

The size of his stake not only prevented Tesco from delisting Dobbies, but it might also enable him to block various key resolutions at annual meetings and EGMs to protect his own position in the gardening sector.

In a statement yesterday, Dobbies added: "The company intends to present a robust defence of its strategy at the court hearing."