"To be happy means to be free and to be free means to be brave," Pericles said in his oration for the Athenian war dead. The ancient Greeks treasured parrhesia, which can translate as "free speech" or "all speech" or "true speech". Whatever version you prefer, it always carried a notion of courage with it.

The 20th-century French philosopher Michel Foucault developed the theme and argued that speech was only free when the weak used it against the strong. In parrhesia, the speaker chooses "truth instead of falsehood or silence, the risk of death instead of life and security, criticism instead of flattery and moral duty instead of self-interest and moral apathy". On Foucault's reading, the worker who criticises his boss uses parrhesia. The boss who shouts down his worker, does not. The woman who challenges religious notions of her subordination is a parrhesiastes. The clerics who threaten her with ostracism or worse are not. In the Chinese legend, the mandarin who knows he must contradict the emperor orders carpenters to build him a coffin and takes it with him to court. Pericles would have approved.

We like to think of ourselves as speakers of truth to power. The British national stereotype holds that we are a sturdy people, who are proud of our right to speak our minds. Our behaviour at work belies the cliche. I know good journalists at News International, but not one of them challenged a management that was presiding over a criminal conspiracy. If they had spoken plainly, their editors would have fired them and in all likelihood they would never have worked in the media again, because no other manager would want them to do to him what they had done to his predecessors.

In their complicity with their superiors, they aped the workers in the City and on Wall Street, who knew that asking awkward questions would ruin their careers. "A risk manager once told me that to raise an issue that undermined the bank's multibillion-dollar profits would have been to 'sign his own death warrant'," a Wall Street derivatives trader said after watching Charles Ferguson's Inside Job. "This inability to challenge trading desks generating billions in phantom profits was endemic." The fate of Paul Moore, a risk manager at HBOS, proved his point for him. James Crosby, its chief executive, made him redundant in 2005 after he warned that the bank was engaged in reckless lending. Moore has never found another job in banking since.

Not one headhunter has even bothered to sound him out for a possible job, despite Moore being the foremost specialist in his field. Crosby, by contrast, prospered until the crash Moore foresaw destroyed HBOS. Gordon Brown was so impressed by his phantom profits he sent him to Buckingham Palace to be knighted by no less a personage than Her Majesty, the Queen.

Keeping mum seems not so dumb in the British workplace until you consider the consequences. The British banking system collapsed in 2008. Last week, we saw how Rupert Murdoch thanked the News of the World's staff for their loyal silence. He protected his compromised son and Rebekah Brooks by sacking the lot of them and closing their paper. Never in the history of British journalism have so many sacrificed so much for so few.

Murdoch will not recognise trade unions because he knows that they are an alternative source of power, which could challenge tyrannical managers. Before you become too misty-eyed about the comrades, however, look at the public sector, where the unions are still strong. Even medics, who have a professional duty to protect the interest of patients, are exposed to the punishments of a hierarchical culture that regards secrecy as a virtue and the free exchange of information as a sin. The British Medical Journal said that when a doctor raised concerns about unsafe heart surgery in his hospital, "his career stalled" and he moved to Australia to find work.

Medical whistleblowers, whose concerns touch on vital questions of who lives and who dies, "find themselves the subject of retaliatory complaints and disciplinary action," the BMJ continued. In one case of alleged research fraud, whistleblowers were advised to "keep quiet or their careers would suffer".

Ealing Hospital's treatment of Sharmila Chowdhury typifies the insouciance with which NHS managers treat public health and public money. It sacked her on trumped-up charges after she accused two doctors of moonlighting. An employment tribunal found in her favour, but rather than reinstate her, the Ealing Hospital NHS Trust prefers to waste taxpayers' funds on paying her off. Like Moore, she has learned that when you challenge one hierarchy, you challenge them all. Sharmila tells me that she was about to land a job with another hospital when its HR department realised that she had broken the omerta of the NHS bureaucracy. The hospital decided it did not want her after all. She remains unemployed and has no way of paying her horrendous debts.

"To be happy means to be free and to be free means to be brave," said Pericles but he did not have work in today's hierarchies. In Britain, the brave are sacked and the rest of us leave our freedoms behind when we enter the workplace. After the bankrupting of the financial system and the disgrace of the Murdoch empire, we need to think of new settlements that stop the private interest in keeping your job overwhelming the public interest in free debate.

The Commons Health Committee is trying to remove the incentives to bite your tongue by asking the General Medical Council and the other bodies that regulate 650,000 NHS clinicians to punish those who decide to keep silent when the interests of patients demand that they speak out. Stephen Dorrell, the committee's chairman, suggests that Britain should move away from the old debates about how to protect whistleblowers. Instead, he wants to look at the mass of workers, who behave honourably themselves, but prefer silence to valour when they see misconduct in their hospitals – and by extension in their schools, corporations, banks and, indeed, newsrooms.

Dorrell's idea is not wholly novel – the government places a duty on lawyers to report the smallest suspicions that their clients may be laundering money. But it provides a sobering comment on the cowardice of the average British citizen. Society cannot rely on us to draw on our own reserves of courage; instead, we need laws and regulations to compel us to be brave or suffer the consequences.

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• This article was amended on 15 July 2011. The original referred to an industrial tribunal. This has been corrected.