Garden centre chain Dobbies was today set for a legal clash with billionaire entrepreneur Sir Tom Hunter over its plans to raise £150 million from shareholders.

Sir Tom, who owns 29.9% of the chain, is attempting to block an open offer announced by the Midlothian-based group in April to strengthen its balance sheet and fund expansion.

Supermarket giant Tesco owns 65% of the chain after a £155.6 million takeover deal last year, although Sir Tom said at the time the deal undervalued the business.

It will cost Sir Tom's West Coast Capital (WCC) investment vehicle around £40 million to take up the extra shares and maintain its stake in the business. If it does not, WCC's holding could fall to around 15%.

Sir Tom is seeking an interim order to block the proposals, although Dobbies said it would make a "robust defence" of its plans at a court hearing. WCC was unavailable for comment.

Dobbies said its proposals offered funding "on attractive terms in current market conditions" and hopes for an early resolution to the dispute to focus on running the business.

The garden centre chain has around £110 million in debt, but is looking for the extra funding to expand the group beyond its current 23 sites, which are split between Scotland and south-east England.

Dobbies made its latest acquisition move with the £8 million purchase of the Sandyholm garden centre at Crossford, in Lanarkshire, last month and further deals are in the pipeline. The group now has almost 2,000 staff.

A Tesco spokesman added: "We are surprised that WCC, which says it is committed to long-term growth at Dobbies, should seek to prevent it raising fresh funds.

"Tesco strongly believes that this open offer is by far the most advantageous means in current markets for Dobbies to raise vital capital for its future expansion."

In the year to October 31, Dobbies posted a 12% fall in pre-tax profits to £3.8 million, as last summer's poor weather hit the business.