Sources suggested headhunters drafted in by C&W have yet to finalise shortlists of applicants for some of the top posts, four weeks after the internal deadline of the end of January.
The news is likely to add to speculation that the complex task of creating the new concern, called C&W Communications, is slipping behind schedule. It is more than four months since the original merger announcement .
Dick Brown, C&W's chief executive, is understood to have set a final deadline of 3 April to complete the merger and bring the business to the stock market.
In public C&W has insisted the target is only to complete the merger by the spring, a much vaguer timescale.
However, the formal offer document for shareholders outlining details of the deal has yet to be completed. Financial advisers are said to be still discussing the position of the minority investors in the new empire which comprise Bell Cablemedia and Nynex CableComms. Bell has already completed its pounds 700m takeover of Videotron which was the precursor to the main deal.
So far C&W has appointed just three board members to run the new business and none of these jobs has gone to Mercury employees. Graham Wallace, the new chief executive poached from Granada's restaurants empire, has been joined by Nicholas Mearing-Smith, finance director of Nynex CableComms and, a fortnight ago, Martin Hayton, personnel director of C&W's majority- owned Hongkong Telecom.
The top firm of global headhunters, Egon Zehnder International, are thought to be compiling a shortlist for the post of director of business communications. One likely candidate is David Sexton, who is in charge of services to Mercury's largest commercial customers. However, other board posts remain to be filled, including the crucial job of running residential telephony and television operations.
Mr Wallace is believed to have said that additional time should be spent finding the best candidates. A spokesman for C&W last night said the process was on target, though he declined to reveal if there were any internal deadlines. "We are planning the next raft of appointments and it is progressing reasonably well."
The challenges come as C&W is thought to be moving closer to an alliance with the Global One partnership between France Telecom, Deutsche Telekom and Sprint of the US, which was one of Mr Brown's previous employers.