More recently, the accountability klieg lights have illuminated the boardrooms of the City of London and Wall Street.

Part-time non-executive directors must also share some of the blame, say the critics, since they often sit on several boards and cannot spend sufficient time understanding each of the companies’ risks. If only directors were focused on the detailed business of just one board, the argument goes, we might avoid another crisis. This line of thinking takes no account of the executive talent that would be driven from boardrooms, the risk to the independence of the full-time director and the lack of diversity that would result.

Earlier this year, Private Eye, the satirical magazine, devoted its back pages to a review of the boards of UK banks and concluded: “Three attempts at a code on corporate governance later, bank non-executives have once again proved the truth of the dismissive comment by Lonrho’s chief executive, RW ‘Tiny’ Rowlands, that they were ‘as useful as baubles on a Christmas tree’.”

Of course, the irony of the argument – that useless directors would be more useful if they only spent more time on board business – is lost on the critics. Nonetheless, Lord Myners, the UK’s City minister, told the House of Lords economic affairs committee: “Non-executive directors at our large banks and insurance companies are going to require more time to the activity than they have in the past and probably will need to be paid more.”

Responding to such criticism at a recent meeting of European board directors, one non-executive director commented: “We are in danger of blurring the distinction between the executive and non-executive director. Are we going to spend two to three days a week per company? I spend one and a half days now, in order to deal with all the data.”

That concern is valid. Nell Minow, the chair of the Corporate Library, a corporate governance research firm, wrote on CNN.com in March: “We call the phenomenon of directors who serve on four or more corporate boards ‘overboarding’. Overboarding can limit the time and attention a director has for each board. It can also be an indicator of – or a contributor to – so many relationships and connections that it makes it more difficult to provide the respectful scepticism necessary for independent oversight.”

How many boards can a director serve on without going overboard? Most regulators have no definitive policy. The UK’s Combined Code on corporate governance doesn’t specify a number, nor do the listing requirements of the New York Stock Exchange. RiskMetrics, the corporate governance adviser, recommends that current CEOs should serve on no more than two outside boards, while other directors should sit on no more than six.

Many companies apply their own limits, including 50 of the top 100 companies in the US (up from 29 in 2004, according to a 2008 survey by Shearman and Sterling, the law firm). However, the limits are still broad, with those companies that specify a number mostly opting for between four and six.

Some directors are taking action to “unboard” themselves, especially if they are sitting CEOs of other companies. According to research in Corporate Board Member, about 50 CEOs in the US quit their outside boards in 2008, including Raytheon’s William H. Swanson, who quit the Sprint Nextel board: “Many cite the economy-induced pressures of their day jobs as their reason for leaving.”

The Board Index produced by Spencer Stuart, the headhunter, for the UK in 2008 reported: “The number of chief executives serving on external quoted company boards has fallen back to its 2006 level.”

What is more relevant is how much time directors spend on each company’s board business. Solid data is hard to come by, but the US National Association of Corporate Directors annual survey for 2008 put the number at an absurdly precise 223.1 hours per year on board and committee business, including preparing for and attending meetings, director education and travel time. Not all those hours could be considered “quality time”.

The actual number depends on how many board committees directors serve on and in what capacity. A chairman of an audit committee will devote substantially more time than a board director who serves as a member of a governance committee. A retired executive will have more time to devote than a sitting CEO.

Directors understand the rising public expectations of their role. Many are concerned about a new standard of perfection being set for their performance that will have a knock-on effect for management and board advisers, such as the external auditor.

A survey in McKinsey Quarterly in February showed that 23 per cent of board director respondents reported holding more frequent meetings as a response to the global economic crisis; 28 per cent predicted that board directors would need first-hand experience of the crisis by visiting customers and distributors. However, when one US director told the 5th Annual Audit Committee Issues Conference in Miami in February that he spent five weeks a year visiting different operations of one bank, the audience of fellow directors was aghast.

The tension is whether a more full-time director can really remain independent. In his 2004 book Boardroom Excellence, Paul P. Brountas, a partner at Wilmer Hale, the law firm, noted that directors “might be inclined to avoid conflict or disagreement in order to keep their jobs and director fees. It is likely that this would be particularly true of retired or unemployed executives and others for whom director fees constitute a major or significant part of their income”.

Another issue will be whether such full-time directors can really bring enough outside experience to the boardroom table. Directors complain that the scenario planning being undertaken by many boards as a mechanism to ensure they survive the credit crisis and the recession is already hampered when conducted by boards packed with industry experts who cannot think outside the sector-specific box. Directors who sit on boards in different industry sectors bring diversity to each of those boards – although the opposite argument, in favour of specialism, is often made for financial services.

Another unintended consequence of a demand for more full-time directors may be the diminution of director talent. If CEOs are already stepping down from their non-executive roles on other boards, and CFOs and other executives will probably follow, there is already a talent gap to be filled.

Full-time directors who are dependent on a company for their income and who are over-focused on one sector, with no other board experiences to draw on, are no more the answer to a shareholder’s prayer than the current set up of imperfect, part-time, non-executives.

The writer is a partner at Tapestry Networks