Speaking at the Great British Workforce Revolution event in London this week, Brennan said even though the rewards for NEDS are high, candidates should consider all eventualities before accepting them.
"These positions are fraught with risk," he said. "You really have to trust the people you're working with. You have to make sure you understand what the board want from you and that your skills are relevant."
The recent View from the top report by global law firm Clifford Chance revealed almost half (47%) of senior professionals would be reluctant to take a NED role because of the risk to their personal reputation.
Brennan agreed that if there are financial problems within a company, a NED member's reputation can easily be dragged down. He also said that taking a director role automatically puts certain information about the holder in the public domain.
"You have to be careful and be very sure that you can explain anything in your past," he warned.
Despite the personal risks, John Whitwell, company secretary of investment bank Daniel Stewart & Co., said NEDs can add value to companies.
"The most valuable are governance experts," he said. "NEDs who are familiar with HR can save you and your company from some pretty hefty legal bills."
He added that he sees the nature of NED positions changing in the future.
"I think they will be better paid and closer to full-time as the level of involvement will need to be much higher," he predicted.
