It also revealed its forward order book was at the record level of £1.2bn.
The consultant reported a revenue of £363.5M for the six months to 30 June 2008, up 40% from £259.8M during the same period in the previous year.
Pre-tax profits were £23M, up 43% from £16.1M in the first half of 2007, with pre-tax profit margins rising marginally from 6.2% last year to 6.3% this year.
"Our strategy of diversification across many different sectors and regions has enabled WSP to continue to deliver outstanding financial results," said a statement by the WSP board.
"With strong organic revenue growth and an order book at June of £1.2bn (December 2007: £0.9bn), we are able to demonstrate our considerable progress so far this year. The order book has benefited from significant public sector transport framework contracts together with major international project awards particularly in the wider Middle East region."
"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% annual revenue growth and 0.5% operating profit margin improvement each year. We remain on course to continue to deliver our Plan for the remainder of 2008 and 2009."