Police have been called in to investigate a con trick which has seen firms asked for confidential financial information by fraudsters posing as government officials.
Fake letters - supposedly from the OGC - have been faxed and emailed to companies, including architects and engineers, hoping to win contracts.
Many major practices in the UK are either on or hope to join preferred procurement lists at the Treasury organisation.
Yesterday, officials at the OGC - an independent office of the Treasury charged with securing value for money from major state projects - warned suppliers to be on their guard.
'The OGC wishes suppliers to know that these requests are entirely spurious, and asks those who receive them to ignore them,' it said in a statement.
'The OGC has alerted the police to the situation and is assisting them in an attempt to stop any further nuisance to supplier organisations,' the statement added.
An OGC spokesman said he was not aware of any cases in which firms had given their bank details to fraudsters.
The letters, although they have used a genuine OGC address, have been signed using fake names, such as 'Dan Jacobs, senior procurement officer'.
The spokesman said concerned firms should call the OGC Service Desk on 0845 000 4999.
Have you been on the receiving end of one of these scams? If so, contact Ed Dorrellto let us know about it.