Hyder's board had accepted a $433.3 million bid from Netherlands-based Arcadis, which also owns the EC Harris building consultancy, on June 31.

However, last week Hyder announced that Nippon Koei had made a $450.5 million all cash counter offer. The offer represents a premium of approximately 44.9 % to the closing price of 469 pence per Hyder share on 30 July 2014.

Nippon Koei has annual revenues of $708 million and earnings of around $57 million. The firm said that acquiring Hyder would allow it to become a "top tier global engineering consultancy".

Its president, Noriaki Hirose, said:

"This merger represents a truly transformational step for Nippon Koei, fulfilling founder Yutaka Kubota's long term strategic vision of broadening the client base and geographic footprint of Nippon Koei, whilst continuing to focus on our core sectors of transportation, utilities and property.

I regret that the confidential nature of our interest has meant that we have not yet had the opportunity to meet many of the employees of Hyder and begin planning our combined journey together."

He added that it planned to make "minimal" changes to either firm's existing structure.

Commenting on the Offer, Ivor Catto, Chief Executive of Hyder, said:

"The cash offer from Nippon Koei announced today represents a 30 pence premium to Arcadis' offer announced on 31 July 2014 and accordingly the Hyder Board is now recommending the cash offer from Nippon Koei. The Hyder Board considers that Nippon Koeis cash offer substantially recognises Hyder's growth prospects, and provides certainty, in cash, to our shareholders today. The merged group should also provide further opportunities for our highly valued employees and clients."

Meanwhile, Arcadis said that it "is considering its position and will make an announcement in due course".

In the year to March 31, the company had revenues of just over $500 million.