Jill Stephen, a former shareholder in Ohio-based company SE Johnson, has claimed in a law suit that the company's former senior vice president and general counsel, Jack Zouhary, bought half her stake in the building materials firm for $440 a share, 15 months before the company was acquired by Oldcastle for $1,700 a share in 2003.

Stephen, who is a granddaughter of SE Johnson's original founder, has claimed that Zouhary and SE Johnson's former company president, Daniel Brown, failed to inform her of internal valuations that had been placed on the company's stock of between $696 and $786 a share.

She estimates that she lost $636,000 as a result of selling her stock at the lower price of $440.

Stephen originally filed the law suit in 2004, but amended it within the past month to include allegations against Zouhary, who was appointed a federal judge by US president George Bush in March.

Zouhary worked with SE Johnson from 2000 and joined a law firm in 2004 before being appointed to the judiciary in 2005.

Zouhary's lawyer is understood to be preparing a vigorous defence of the law suit.

Zouhary revealed during the vetting process for his federal judge nomination that he could become a named defendant in the case.

SE Johnson provides paving, heavy highway and bridge construction materials in northern Ohio, southeast Michigan and northeast Indiana. When CRH acquired the company, it disposed of some non-core assets, reduced its exposure to non-paving related highway and bridge construction, and integrated the unit into the Ohio-based Shelly Group and Michiganbased Thompson-McCulty.

Last March CRH announced a 15% rise in net income to 998m for 2005, and a 13% rise in sales, to 14.4bn.

In the past two years CRH, Europe's third-biggest building materials firm, has spent 2.6bn on acquisitions. Last April it paid $350m to buy US-based MMI Products, while last month it paid 170m to buy German construction equipment firm Halfen-Deha.