Thanks to Leveson the job of journalists has become that little bit harder

Foreign experience shows harsher press rules in the UK will play into the hands of the rich and powerful

At risk: Journalists filming wounded Free Syrian Army soldiers (ABACA/PA)

There is something chilling about the fecklessness with which the leaders of Britain's three main parties propose to weigh down the press with a battery of regulations. Reporters in the Middle East have generally been more concerned about being shot or kidnapped by targets of criticism than being sued by them. The chance of anything this dire happening to a foreign journalist is not high compared with the horrific casualty rate among local reporters (151 journalists murdered in Iraq since 1992, 84 per cent of them Iraqis), but the possibility is still there.

The few who have threatened legal action over something I have written tend to be very rich individuals, or else an individual acting on behalf of an oil state. The purpose of these legal threats is usually to create an atmosphere of intimidation in which writing about a single individual or country may not seem worth the risk if expensive legal troubles are going to ensue. Those adopting this strategy have been depressingly successful in disappearing off the international media map. Harsher press regulation in Britain simply adds to the ample legal armament available to the lawyers of the rich and the powerful wherever they live.

The extreme difficulty of investigating such people is underestimated by non-reporters, whose knowledge of investigative journalism is drawn from films such as All the President's Men about Watergate, or The Pelican Brief about pursuit of a murderous Louisiana oil billionaire. In movies like these, the reporter is typically chided by his crusty but benevolent editor for not producing proof of crimes and threatened with removal from the story. After pleading with his superiors, the journalist is grudgingly given an extra 24 or 48 hours to bring his investigation to a successful conclusion, which he or she invariably does.

If only it were that easy. Legal risk, time and expenses measured in months and years rather than days help to explain why, outside the cinema, there are so few serious journalistic investigations into the wealthy and powerful. And when investigations do happen they appear in a handful of publications such as Private Eye. It is impossible to quantify with any precision, but by one estimate between a quarter and a third of real scoops in Britain – as opposed to celebrity tittle-tattle – over the past 50 years have appeared first in Private Eye.

Journalists have great ability to publicise crime, but not to uncover it because they lack the legal powers to do so. Every journalist learns early on that people do not generally say anything that would land them in trouble, still less in jail. The absurd advice "follow the money", given to Bob Woodward and Carl Bernstein when investigating Watergate, supposes that banks are willing to disclose information about their clients, which they are not except under legal duress. Contrary to Watergate mythology, the scoops attributed to Woodward and Bernstein stemmed almost exclusively from deliberate leaks by those with the power to subpoena individuals and documents, such as the FBI. Of course, The Washington Post reporters played a crucial role in publicising these discoveries, but successful investigation was necessarily the work of others.

Few of these and other difficulties facing the investigative journalist are new. In 1933, my father, Claud Cockburn, set up an anti-fascist newsletter called The Week in an attic room in Victoria Street containing a kitchen table, four chairs and a smaller table. His accommodation was so modest because he had only £40 to spend, but, making a virtue of necessity, he believed that "most libel actions are brought for the purpose of getting money, and it would be evident to one and all that we had no money at all". In the event, his newsletter flourished for many years and he was never successfully sued.

The difficulty in obtaining information about the actions of the powerful, without their co-operation, means that the media is the conduit of news more frequently than self-respecting journalists admit. Nobody tells the reporter anything for nothing, the motive of a source most usually being personal and institutional advancement or rivalry. This tends to be downplayed by reporters, who feel that their source's credibility will be enhanced if the reader is left to suppose that he or she is motivated solely by a desire to serve the public good. For instance, earlier this month, just as Britain and France were lobbying to amend the EU ban on arms supplies to the Syrian rebels, news agencies published a flood of disclosures by unnamed diplomats about increased arms supplies to Syrian government forces from Russian and Iran. Suspicious signs in stories like this are an excessive quantity of supportive detail and confirmatory quotes from supposed experts from Washington or London think tanks whose qualifications to confirm the truth of the story are hazy.

Happily, the outlook is not quite as bad as this might sound for journalistic revelations. In Britain, dissident reporting is far easier when the political elite and the media are divided. Thus it was that my sceptical articles about the occupation of Iraq after 2003, passionately opposed by many, got a generally friendlier reception than similar ones about Nato's war in Libya in 2011, which was almost universally approved.

Greater state regulation of the media in Britain matters because the exercise of press freedom often depends on knife-edge decisions that reflect the will, independence and capacity of newspaper or broadcaster. The decline of the US press in recent years is characterised by its treatment of Bradley Manning, the young US soldier who wanted to release an archive of official documents to which he had access. The New York Times had published the Pentagon Papers in 1971 and The Washington Post had pursued the Watergate investigations in the face of furious government denials in 1972. But 40 years later, reporters on these two leading US papers either did not return Manning's calls or rebuffed his offer of information, compelling him to give his information to WikiLeaks.