Google’s proposed £650m UK headquarters at King Cross has been delayed by “at least” three years, the boss of the firm appointed to build the high-profile office has admitted.

Google’s design review of its planned £650m UK headquarters at King’s Cross – first announced last November – is expected to take as long as two years, amid a wider review of the tech giant’s planned large-scale developments worldwide.

However, now it has emerged that Bam Construction, which won the £300m main contractor role on the 750,000ft2 project in March 2013, expects construction on the project will not begin until “at least 2017”, three years later than the original start date of early 2014.

Google announced last November that it had decided to scrap the design for its £650m HQ in King’s Cross (pictured) in a move the firm said was aimed at “challeng[ing] ourselves to do something even better”.

Architect Allford Hall Monaghan Morris has been retained to rework the design of the 750,000ft2 scheme, with cost consultant Gardiner & Theobald and engineer Waterman also continuing in their roles.

The tech giant did not give a time frame for the review.

Publishing its accounts for the year to 31 December 2013 today, Bam said that while it was “delighted” to have been appointed as preferred bidder for the Google HQ job, it was “disappointed” that the project had now been delayed.

Cash said Bam was continuing to provide “sustainability consultancy to Google, assisting them to redefine the sustainability vision for the new headquarters”.

However, it is understood that Bam no longer considers the job as part of its pipeline and expects the project to ultimately be put back out to tender.