Many trustees of voluntary bodies serve on as many as four other boards.
A recent survey of 129 trustees, carried out by Watson Wyatt investment consultants, found that 28 per cent of them sit on more than five boards.
Although this study was based on a small sample, research by the Charity Commission that showed 62,361 trustees sit on more than one board confirms the trend. This latter survey also showed that 1,713 trustees sit on more than five boards.
These figures raise a number of issues, particularly with regard to diversity.
Neville Brownlee, head of regulatory reports at the Charity Commission, says: "We do come across examples of charities where the board of trustees is simply not diverse enough, and we would like to see more of a mix.
"We know that a lot of charities still go by word of mouth and recommendations when recruiting trustees, but we would encourage them to use the local press and be more creative in the way they advertise," he adds.
Brownlee believes development of trustees should not end with the recruitment process: "Our research shows that most charities give their new trustees the accounts, the governing document and previous minutes when they join. But too many still don't. If you want to keep your trustees on, you need to get them involved."
Charities that are happy to hire trustees who already sit on other boards may make fewer demands on their time. But many expect greater involvement.
Ben Summerskill, chief executive of Stonewall, which earlier this year advertised trustee posts for the first time, says: "We do not expect our trustees to meet only four times a year; we expect them to engage with the organisation without interfering. I don't think someone can do this efficiently for us, as well as for four other charities at the same time. We turned down some applicants because they did not have the time we would expect them to dedicate to the role."
At Victim Support, vacancies for trustees are also advertised, but this is intended to improve diversity, rather than prevent individuals taking up positions on several boards. Helen Reeves, chief executive, says: "In some cases we regard it as an advantage if applicants already have positions on other boards. It is a sign of experience."
Reeves blames the duplication on a lack of applicants. She says: "Sometimes, the requirements of the position can sound quite daunting. I think the role of trustee needs to be promoted by the sector in order to encourage new people to consider it."