Head of external comms Chris Rumfitt will leave at the end of the month. He is currently in discussions with a number of London-based corporate and public affairs agencies.
Network Rail has been widely criticised for the travel chaos that hit commuters at the start of this year when two of Britain's busiest lines were closed by late-running engineering works.
Its directors are likely to be hauled before the Commons Transport Select Committee to explain the fiasco on the West Coast Main Line that disrupted the travel of 60,000 passengers a day. The select committee is expected to take a highly sceptical view of comments from Network Rail that American project manager Bechtel - a company held in high regard by government ministers - was largely responsible for the chaos.
Network Rail does not have a retained agency for PR and Rumfitt's decision to quit increases the likelihood that the company will turn to agency backing if pressure continues to mount. However, head of media relations Kevin Groves insisted this is not on the cards at present.
Rumfitt joined Network Rail five years ago, having previously been an account director at Weber Shandwick. He oversees both Network Rail's media relations team, headed by Groves, and its public affairs team, headed by Garry White. Rumfitt reports to government and corporate group director, Victoria Pender.
Network Rail is yet to appoint a replacement for Rumfitt, who resigned before Christmas. It is understood that two internal candidates have shown interest, but Network Rail is keen to recruit a heavyweight external candidate to help salvage its reputation in Westminster and among the general public.