The Omnicom companies Claydon Heeley Jones Mason and Agency.com are joining forces to launch an operation called Agency Republic.
Agency Republic, which will operate as a joint venture between the two companies, will be headed by Scott Gustlin, the former managing director of Agency.com in London and now its vice-president of European operations, and Martin Brooks, the joint managing director of Claydon Heeley Jones Mason.
The agency will combine digital and traditional marketing expertise.
It is expected that between 15 and 20 Agency.com staff in London will join the new agency, together with staff from Claydon Heeley as well as new hirings.
Claydon Heeley's chairman, Jon Claydon, is believed to have been talking for the past year to Agency.com about a possible joint venture. The two agencies have clients in common including British Airways.
Omnicom owns a minority stake in Agency.com, which is one of the largest global digital solutions companies with clients including Visa and One2One.
However, last year it was forced to make redundancies in a bid to cut costs and remain profitable.
The launch of Agency Republic follows similar attempts by traditional direct marketing companies to forge partnerships with digital agencies.
Last year, Evans Hunt Scott merged with Real Time and BHWG Proximity has an alliance with Traffic. Omnicom is looking at ways of creating closer relationships between its other online and offline agencies.
Gustlin refused to comment on the agency launch but said: 'We have enjoyed a good relationship (with Claydon Heeley) working on a variety of clients.' Claydon was unavailable for comment.