The agency was hired following the recent selection of St Luke's to handle creative for a campaign that will break this month to support Britax's range of King car seats.
M2M is expected to focus on implementing a media strategy that will target parents through TV and online activity.
St Luke's was appointed in November to handle creative after a two-way pitch.
The last major push behind the Britax brand came in 2000 through the now-defunct agency Barrett Cernis.
Matthew Turner, the UK trade marketing manager of Britax, said: "Through this campaign, we will be speak-ing directly to consumers about the importance of buying a high-quality child car seat and fitting it correctly to ensure children are fully protected."