A Kent company with sales of £3.5 billion over the last year is now the UK's fourth biggest family-owned business.

Construction firm Laing O'Rourke, whose head office is at Crossways, Dartford, "had a strong year of growth," says the Institute of Family Business (IFB), which has just published the results of its Top 10 UK Family Business Survey.

The company, which is owned by the O'Rourke family, increased sales by £1 billion compared with the previous year.

IFB director general Grant Gordon said: "The UK has seen difficult trading conditions in the last year, but there have been some remarkable success stories among the UK's top family businesses."

The top family business was Associated British Foods (ABF), owned by the Weston family. It increased sales to £10.2 billion, compared to £9.3 billion the previous year.

Chairman of Laing O'Rourke is Ireland-born Ray O'Rourke, who came to Britain in 1967 and initially found work as a labourer . After setting up his own business as a sub-contractor in 1978 in his family's garage his company has gone on to become the UK's biggest privately-owned construction firm.

The company is involved in some of the UK's highest profile building projects. The business has grown spectacularly since the acquisition of John Laing in 2001 and has 20,000 employees, but it remains a family concern with Ray O'Rourke as chairman and chief executive and his brother Des the joint deputy chairman.