Europe's agencies are telling clients that they must drop their rigid policies on account conflict - or be prepared to pay premium prices in exchange for exclusivity.
They claim that the hard line taken by some clients over conflict is no longer sustainable as the ad industry and client companies consolidate and are an unjustifiable restraint of trade.
Now the European Association of Communications Agencies is issuing guidelines on account conflict to bring advertising in line with other service industries.
Industry leaders agree that the guidelines cannot be imposed but hope they will be accepted and followed in the same way that the ground rules for the conduct of pitches agreed by the IPA and ISBA, the advertisers' trade body, are followed.
The guidelines are understood to have the informal support of senior executives at ISBA as well as the backing of the UK's leading pitch consultants.
Andrew Melsom, the managing director of Agency Insight, warned: 'Unless clients can accept the principle of conflicting accounts in the same building, we will run out of competencies.'
David Wethey, Agency Assessments International's managing director, said: 'It is legitimate for an agency to put a premium price on exclusivity.'
The EACA claims the security risks for clients resulting from conflict are exaggerated and calls on agencies to do more to convince clients that 'Chinese walls' really work.
Rupert Howell, the IPA's president, said: 'Matters have reached such a stage that financial services clients looking for a top 30 agency face an impossible job if they are not prepared to accept conflict.'