Tensions between Omnicom and Channel 5 ratcheted up last week when the broadcaster sent an uncompromising letter to all of the agency group’s clients, asking them to seek "independent advice" about their media. Dust-ups between media’s trading boys are not new. However, the situation between Channel 5 and Omnicom appears to have taken the industry into uncharted waters. Omnicom shops spent nearly £50 million on Channel 5 in its last full year. The broadcaster has not received any advertising since last summer and now feels it has nothing to lose.