The updated guidelines not only allow agencies to protect their rights and limit their liability for insurance purposes, but provide clear advice to clients on what they should do to keep control of copyrighted material.
They replace an earlier version published in 1998 and have the backing of the IPA and ISBA.
The other major signatory is the Chartered Institute of Purchasing and Supply, acknowledging the increasing role of purchasing managers in agency selection decisions.
Brinsley Dresden, a partner at the law firm Lewis Silkin, who drew up the contract, said: "With so much instability in the market at the moment as clients look for cheaper deals, it's never been more important for agencies to know their rights."
The guidelines incorporate recent legislative changes including acts covering data protection and financial services. All three trade bodies are stressing the importance to members of using the updated proposals as a template.
"Agencies will increasingly find that insurers are insisting that they have proper housekeeping measures in place, Dresden added. "If there is a dispute about a piece of work and an agency wants to claim on its professional indemnity insurance it will need to show it has a proper contract in place to limit its liability."
For clients, the guidelines clarify the position on copyright. "Even if you've paid for copyrighted work it doesn't necessarily belong to you," Dresden said. "It has to be signed away by the agency."