Is there such a thing as a public service ethos? Are people in the public sector driven to work hard because they care rather than merely because they are paid to? Since the advent of Thatcherism, the assumption underlying nearly all policy has been that this talk of an ethos is just a con, that, as David Marquand has put it, public sector employees are "self-interested rent-seekers, trying to force the price of their labour above its market value".

To use the distinction made by the former Downing Street adviser Julian Le Grand, teachers, doctors, nurses, social workers and civil servants are just knaves like the rest of us, not knights motivated by public-spirited altruism. That is why we need targets, league tables, performance-related pay and all the other paraphernalia of post-Thatcher bureaucracy. It is another example of the belief that everybody's behaviour is reducible to economic stimuli. We are all just sophisticated versions of a chimpanzee that will do whatever it takes to get the banana.

Now comes research from the Centre for Market and Public Organisation at Bristol University suggesting the public service ethos is not a myth (see Research in Public Policy, Spring 2008, and http://www.bris.ac.uk/Depts/CMPO/workingpapers/wp197.pdf [2]). It finds that, in education, health and social care, 46 per cent of employees in the non-profit sector do unpaid overtime against 29 per cent in the private sector and that, on average, they put in more than an hour extra a week (nine hours 35 minutes against eight hours 20 minutes).

To some extent, the difference can be explained by age, gender, dependants, job type, unionisation, tenure, promotion prospects and so on. But even when all such factors are taken into account, those in the non-profit sector are still significantly more likely to be slaving at their desks beyond the contracted hours.

The Bristol researchers estimate that the public sector gets an extra 120 million hours at no cost, equivalent to 60,000 employees (or 2.4 per cent of the public sector workforce in education, health and social care) working for nothing. They suggest, however, that the explanation lies in the individuals themselves, rather than in the expectations and norms of the different sectors. Those who switch sectors don't then change their working habits. For example, people who moved to profit-making concerns had been less likely than their public sector workmates to do unpaid overtime. Nor is there any evidence of a general "non-profit" effect. Outside the caring professions, there were no differences between employees in different sectors.

I am not sure these are very comforting conclusions. The data is taken from official surveys in the 1990s. At that time, I suspect, schools, hospitals and social services were the last bastions of the public service ethos. Now, even those sectors have suffered increased marketisation and privatisation. What Marquand described as Thatcher's Kulturkampf against the public realm has been more or less completed by new Labour. No doubt there are still people who work hard simply because they care, but targets and other controls are now so deeply rooted that it has become almost impossible to identify and celebrate altruism even if it exists.

As Marquand pointed out in his book Decline of the Public (Polity, 2004), the principles and ideals of the public domain once extended far beyond what was state-owned and state-controlled. The belief that, as Marquand puts it, "professional pride in a job well done or a sense of civic duty" might trump "the hope of gain" first flourished in the 19th century, when the state sector was very small. In the 1950s, it was evident in large private sector firms and among certain professional elites, such as lawyers and bankers, almost as much as it was in the public sector. For at least a century, the values of the public realm seeped into the market domain. Now the reverse is happening: market values dominate even non-profit organisations.

Politicians are reaping what they sowed. They, too, are assumed to be knaves rather than knights, their motives subject to constant, hostile scrutiny. The Daily Mail commentator Peter Oborne writes of "the political class" which, regardless of party, has its own distinct interests and attitudes. He strikes a chord. For example, proposals for green taxes are widely dismissed as attempts by the political class to raise more revenue for its own selfish purposes.

All this, I think, helps to explain why Gordon Brown is in such deep trouble. He is a politician out of his time who really does believe in such old-fashioned concepts as service, altruism, civic duty and the public domain, though he finds it hard to express them and harder still to apply them. He probably puts in more unpaid overtime than anybody in the country. Much good it will do him.