Pre-tax profits soared 79 per cent to £28.4 million up from £15.9 million in 2007.
Turnover jumped 40 per cent for the first half to £363.5 million up from £259.8 million for the same period in 2007.
WSP said that its order book was bolstered by public sector transport framework contracts and major international project awards, mainly in the Middle East.
The firm said: “We are in the fourth year of our 5 year strategic plan and the results announced today demonstrate that we are ahead of our published headline financial targets of 15 per cent annual revenue growth and 0.5 per cent operating profit margin improvement each year.
“We remain on course to deliver our plan for the remainder of 2008 and 2009.”