Treasury officials have toned down guidance that is due to recommend “prime contracting” as a key form of public sector procurement.

New advice to civil servants due to be launched by Treasury minister Alan Milburn at a conference on 16 June will also call for more emphasis on design.

Treasury head of procurement Mike Burt said prime contracting, where one party is appointed to integrate the supply chain with an emphasis on whole-life costs, is still relatively untested.

To reflect this, it is recommended as one of the innovative forms of procurement the Treasury wants civil servants to use, but with a warning that it is still in its early stages.

The Ministry of Defence has used prime contracting on two small gymnasium projects, but apart from these, the concept is largely untried. Burt said that the caveat about its use would be removed after more testing.

After intense lobbying from consultants, the Treasury has also beefed up recommendations on the importance of design. Burt said civil servants will be urged to consider a building’s functional, aesthetic and environmental design during procurement.

Design-and-build and prime contractors will also be told that good design will be a key factor in their appointment.

Construction Industry Council chief executive Graham Watts welcomed the revisions to the draft Treasury guidance.