Nuttall has terminated its contracts with three of its suppliers on the Olympic Park site.

The company, which has a £200m contract to handle groundwork and remediation on the project, has parted company with two plant suppliers and a labour provider. It is understood that the firms, which have not been named, left the project last week.

Site sources this week linked the purge to an investigation being carried out by KPMG into alleged infringements of employment practices and conditions by contractors working on the Park.

This was denied by Nuttall. A spokesperson said: “Nuttall has been rationalising its use of plant and labour-only subcontractors as a result of the different type of work that we are undertaking. On this basis we have terminated our contracts with the suppliers. This action has nothing to do with the audit.”

Nuttall brought KPMG in this month to look at working practices and conditions and how labour is recruited to the project. The audit, which is still continuing, was a response to union claims that some subcontractors on the site were not adhering to employment terms set out by the Olympic Delivery Authority.

This week, a BBC investigation separately alleged that hundreds of eastern European workers had fallen victim to a scam promising them non-existent jobs at the 2012 site.

It reported that more than 500 Slovakians paid deposits of £600 to a rogue recruitment consultant on the promise of accommodation on a cruise ship in Docklands and jobs on the Olympic Village site, which did not materialise.

Olympics minister Tessa Jowell has said she will work with police to investigate the matter.