The Public Contracts Regulations 2006

Statutory Instrument 2006 No. 5 The Public Contracts Regulations 2006 came into force january 31st 2006.

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In particular S43 is of interest —(1) Subject to the provisions of these Regulations, a contracting authority shall not disclose information forwarded to it by an economic operator which the economic operator has reasonably designated as confidential.
(2) In this regulation, confidential information includes technical or trade secrets and the confidential aspects of tenders.

In terms of FOIA 2000, this would work as a "prohibition on disclosure" under Section 44.