Catlin could be hit with further resignations in the next month after the launch of a new Lloyd's syndicate, Ark Syndicate Management.
Ark, which specialises in marine, energy, property and casualty insurance, is headed by former Wellington chief underwriting officer, David Foreman.
Speculation is now mounting that further ex-Wellington employees could leave Catlin to join Foreman, who retired from Wellington in April 2006.
Catlin has been hit by a raft of resignations by the Wellington staff, after it bought the company last October for £591m.
A market source told Insurance Times: "My suspicion is that when the Wellington bonuses are paid in April more will follow them out of the door."
It is understood that Foreman, Ark's chief underwriting officer, has already been joined by Peter McIntosh, an underwriter in Wellington's marine hull, cargo and specie division.
Ex-Wellington colleague JP Wells, who specialises in international property, is also understood to have joined Ark.
Ark, led by former head of insurance at Aspen, Ian Beaton, who will become chief executive, will begin operations in April 2007 and write £114m of business.
It is backed by two private equity companies, Aquiline Capital Partners and Lehman Brothers Co-Investment Partners, together with Whittington Group and Swiss Re.
Jeffrey Greenberg, managing principal of Aquiline, and one part of the Greenberg insurance dynasty, will become chairman of the Bermuda-based group, Ark Insurance Holdings.
Greenberg was the former chairman and chief executive of Marsh before resigning in October 2004, after the firm was charged with bid-rigging following an investigation by Attorney General Eliot Spitzer.