Investor chief executive Marcus Wallenberg rejects Mr Ebner's calls

Mr Ebner also wants Investor to buy back shares to boost the value of the remaining ones, and again the Wallenberg family says no.

Investor chairman Percy Barnevik and chief executive Marcus Wallenberg both insist that Mr Ebner, who controls more than 10% of shareholder votes, should focus on the performance of the business rather than its shares, Swedish media reports quoted on Investor's website said.

Investor insists that its shares have outperformed Sweden's main stock market index, both in the past year, the past 10 years and the past 20 years, the reports said.

Ebner will not go away

Mr Ebner's attack on the way the Wallenberg family goes about its business is more than just benign criticism from an outsider.

This is not only because of his reputation as a shrewd businessman with an eye for restructuring businesses but also because his criticism is tough to counter, given the large discount the markets place on Investor shares.

In other words, Investor's share price is lower than the combined net value of its assets.

Many investors are loath to buy into the family-controlled company, essentially because most Investor shares available carry fewer voting rights than the preferential shares held by the family.

As a consequence, even owners of large stakes in Investor may have very little influence.

Intrinsic value

But Investor owns controlling equity stakes in a wide range of leading Swedish multinational companies.

These include the health care group Gambro, the mobile phone firm Ericsson, the engineering company ABB and the drugs firm AstraZeneca.

Buying back shares could be an effective way of boosting Investor's share price.

And if the company was then split in two, it would become more transparent. This too should push its share price up.

Mr Ebner would favour a solution along these lines.

But making it happen in the face of staunch resistance from the Wallenberg family will not be easy, analysts said.