The former director and deputy chairman of the building products group, Kingspan, Mr Brendan Murtagh, is understood to have sold shares worth almost £22.8 million (€29 million) in the company in late trading yesterday.

Mr Murtagh placed the shares with various institutions and an official statement from the company is expected to be made to the Stock Exchange on Monday. It is understood Mr Murtagh offloaded about 12.8 million shares valued at €2.27 (£1.79) a share.

The shares represent some 7.7 per cent of Kingspan's equity, although it is estimated that Mr Murtagh retains about 8.5 million shares in the company, which is a stake of almost 5 per cent. Mr Murtagh was not available for comment last night.

Mr Murtagh has sold shares in the market before. For example, last June, he sold 2.5 million shares for £7.8 million when ABN AMRO stockbrokers placed them with various institutions.

Mr Murtagh was a client of the failed stockbroking firm, MMI, which went into liquidation in early February with total debts of £14 million. He is understood to have owed a substantial sum to MMI in relation to a share transaction, although sources have previously said that the money was not due for payment when MMI went into liquidation and only fell due for payment subsequently. The amount owed to MMI was only a fraction of the sum raised through the sale of the Kingspan holding.

Mr Murtagh resigned as a director of Kingspan in December following share dealings by people connected to him in a targeted takeover company - Hewetson plc.

The dealings in Hewetson shares were made in the name of the wife of one of Mr Murtagh's sons and in the name of a close friend of the other son, after Kingspan had begun due diligence and signed a confidentiality agreement with Hewetson. Mr Murtagh made a capital profit of £23,850 from the sale of the 30,000 shares in Hewetson.

Several directors of the company have been selling shares in the market in the last year.

For example, when Mr Murtagh sold his shares in June, he was joined by three other executive directors. Mr Eugene Murtagh sold 4.7 million shares worth £14.5 million, Mr Eoin McCarthy sold 1.25 million shares for £3.9 million, while Mr Dermot Mulvihill sold 100,000 shares for £310,000.

It is not known whether Mr Murtagh intends to use the money to build up his other investments. He is a significant investor in the property group, Howard Holdings, which is due to list on the Dublin market shortly. He also has extensive interests in several smaller private companies, some of them located in Co Cavan, where Kingspan is based.

The transaction had no major effect on the company's closing share price yesterday, which was up 5 cents (4p) at €2.40 (£1.89).