Senior assistant Stephen Lerner, who claims to be the group head, handed in his resignation last week and will move to Clifford Chance as a senior assistant.
However, a Cameron McKenna spokesman plays down the departure, saying Lerner was not the group head because he was not a partner.
The telecoms group was set up by Cameron McKenna last year and contains nine lawyers, some of whom are partners.
Clifford Chance has one of the strongest telecoms departments in the London market and it is believed that Lerner has decided to move for the greater opportunities which the firm offers.
He refused to comment on whether any clients would be moving over to Clifford Chance with him.
A spokesman for Cameron McKenna explained that it was the policy within the firm that the partner who is in charge of the assistant should be the one to comment on his departure. Lerner's partner in charge, Paul Lush, is on holiday.
But the spokesman says that the telecoms group had made some recent recruitments and that clients would not be following Lerner.
Clifford Chance telecoms partner Tim Schwartz says: "We are looking forward to Stephen becoming an integral and valuble member of our long-established international telecoms practice."