The deal could still be trumped by rival US consultant CH2M Hill, which said it had undertaken due diligence on Scott Wilson and was considering making a cash offer shortly.

Under the terms of the URS agreement, shareholders of Scott Wilson will receive 210p in cash for each share, valuing the firm at £161m.

Scott Wilson shares flew up 87% to 224p this morning on news of the offer, which represents a 76% premium on Scott Wilson’s Friday close.

Geoff French, chairman of Scott Wilson, said: “The Board believes that a combination with URS will significantly enhance Scott Wilson’s business opportunities and represents a compelling proposition for our shareholders, clients and employees.

“This offer reflects the underlying value of Scott Wilson’s business and provides our shareholders with an opportunity to realise that value in cash today.”

He added that being part of an enlarged, global group would open the opportunity to staff to participate in larger and more complex projects.

Hugh Blackwood, group chief executive of Scott Wilson, will join URS’ management committee and will oversee from London the combined international operations for U.K./Ireland, Europe, Middle East, India, and China.

Other members of Scott Wilson’s executive management team will have roles with URS, which will be finalised when the deal is complete.

Scott Wilson has more than 5,500 employees at a network of 80 offices around the world, including offices in key regional centers such as London, Hong Kong, New Delhi, Warsaw and Dubai.

Last year Scott Wilson sales hit £340m generating a profit of £13.6m.