Almost everything is fake. The brave proverbs with which we were brought up – the truth will out, cheats never prosper, virtue will triumph – turn out to be unfounded. For the most part, our lives are run and our views are formed by chancers, cheats and charlatans. They construct a labyrinth of falsehoods from which it is almost impossible to emerge without the help of people who devote their lives to navigating it. This is the role of the media. But the media drag us deeper into the labyrinth.

There are two kinds of corporate lobbyists in the UK. There are those who admit they are lobbyists but operate behind closed doors, and there are those who operate openly but deny they are lobbyists. Because David Cameron has broken his promise to shine "the light of transparency on lobbying in our country and ... come clean about who is buying power and influence" we still "don't know who is meeting whom. We don't know whether any favours are being exchanged. We don't know which outside interests are wielding unhealthy influence ... Commercial interests – not to mention government contracts – worth hundreds of billions of pounds are potentially at stake." (All that was Cameron in 2010, by the way) At the same time, the media is bustling with people working for thinktanks which refuse to say who is paying them, making arguments that favour big business and billionaires.

Perhaps the most prominent is the Institute of Economic Affairs. Like most groups of this kind, it refuses to disclose its funding. But there's a trail of smoke. We now know that it has been taking substantial sums from British American Tobacco (BAT), Japan Tobacco International, Imperial Tobacco and Philip Morris International. BAT has funded the institute since 1963. By pure coincidence, the institute has fiercely defended the tobacco companies from efforts to regulate their products.

In their indispensable new book A Quiet Word, Tamasin Cave and Andy Rowell explain why corporations want other people to front their campaigns. "The third party has the credibility of looking independent, seems to be motivated by something other than self-interest and profit and therefore has a much greater chance of being believed. Credibility, authenticity and the impression of independence are key. It is about separating the message from the self-interested source." While many controversial companies use this tactic, it is particularly important for tobacco firms; first because no one trusts them and, second, because they are banned from seeking to influence public health policy, under the Convention on Tobacco Control, which the UK has ratified.

Last year a presentation made in 2012 by Philip Morris (which sells Marlboro and other brands) was leaked. It explained how the company intended to fight the proposed plain packaging rules in the UK. Plain packaging is a misnomer: the packs show only horrible photographs of medical conditions caused by smoking. The evidence suggests that plain packaging is a powerful deterrent. Philip Morris listed the arguments that should be made in the media to try to prevent the government from introducing it, identified the BBC as a key outlet, and named the Institute of Economic Affairs and the Taxpayers' Alliance as potential "media messengers".

So you might imagine that the media – and the BBC in particular – would exercise a certain amount of caution when interviewing thinktanks funded by tobacco companies about the regulation of tobacco. Such as disclosing that they are, er, funded by tobacco companies. You would of course be wrong.

At the end of last year, Radio 4's Today programme interviewed Mark Littlewood, the head of the IEA, about plain packaging. It failed to inform listeners that the IEA has received funding from tobacco companies. Littlewood, the director of the institute, used two of the arguments recommended by Philip Morris in that leaked document: there's no evidence that plain packaging affects the number of people who smoke, and it stimulates a black market in cigarettes.

I encouraged readers to complain, on the grounds that the BBC's failure to disclose his interests in the issue he was discussing flatly contravenes three of its editorial guidelines. The BBC's responses astonished me. First it claimed that it was not "appropriate or necessary" to include this information, on the grounds that the IEA doesn't publish it. In other words, if you're not candid about who funds you, you're off the hook. Then, as the complaints continued, it maintained that "all we have to go on are newspaper reports. In the absence of any independent verification therefore, it remains an allegation."

When the BBC was told that tobacco companies have admitted funding the IEA, the reasoning changed again. Now it argues that it would be wrong to assume "that an organisation adopts a particular position on an issue because it receives funding from an interested party": it might have formed the position first and received the money as a consequence. That's true, though it's hard to see what difference it makes: if thinktanks survive and prosper because their position just happens consistently to align with the grimmest of corporate interests, the politics of the relationship don't change very much. In either case, surely listeners should be allowed to make up their own minds. Who would not wish to be told that an organisation whose spokesperson is defending Big Tobacco on the Today programme receives money from Big Tobacco? What kind of broadcaster does not see that as relevant information?

Since then, the IEA's staff have been interviewed by the BBC about tobacco eight more times. In none of the interviews I have listened to were their interests declared. It's all about to blow up again, as the government's review of plain packaging reports at the end of this month, and the thinktanks will be trundling all over the media. The petition I published on change.org , calling on the BBC to disclose its contributors' financial interests, has 11,000 signatures so far; if they reach 20,000, I'll present it.

Stories like this remind me that much of life is a struggle against disappointment. Perhaps I'm an idiot, but I expected a world that was so much better. I still believe it's possible. But getting there requires a daily struggle against those who would mislead us.

• Twitter: @georgemonbiot. A fully referenced version of this article can be found at Monbiot.com