What happens to people when they become government science advisers? Are their children taken hostage? Is a dossier of compromising photographs kept, ready to send to the Sun if they step out of line?

I ask because, in too many cases, they soon begin to sound less like scientists than industrial lobbyists. The mad cow crisis 20 years ago was exacerbated by the failure of government scientists to present the evidence accurately. The chief medical officer wrongly claimed that there was "no risk associated with eating British beef". The chief veterinary officer wrongly dismissed the research suggesting that BSE could jump from one species to another.

The current chief scientist at the UK's environment department, Ian Boyd, is so desperate to justify the impending badger cull – which defies the recommendations of the £49m study the department funded – that he now claims that eliminating badgers "may actually be positive to biodiversity", on the grounds that badgers sometimes eat baby birds. That badgers are a component of our biodiversity, and play an important role in regulating the populations of other species, appears to have eluded him.

But the worst example in the past 10 years was the concatenation of gibberish published by the British government's new chief scientist on Friday. In the Financial Times, Sir Mark Walport denounced the proposal for a temporary European ban on the pesticides blamed for killing bees and other pollinators. He claimed that "the consequences of such a moratorium could be harmful to the continent's crop production, farming communities and consumers". This also happens to be the position of the UK government, to which he is supposed to provide disinterested advice.

Walport's article was timed to influence Monday's vote by European member states, to suspend the use of three neonicotinoid pesticides. The UK, fighting valiantly on behalf of the manufacturers Syngenta and Bayer, did all it could to thwart the nations supporting this partial ban, but failed.

Here's how he justified his position. First he maintained that "there is no measurable harm to bee colonies … when these pesticides have been applied on farms following official guidelines". This statement is misleading and unscientific. The research required to support it does not exist.

The government carried out field trials which, it claimed, showed that "effects on bees do not occur under normal circumstances". They showed nothing of the kind. As Professor Dave Goulson, one of the UK's leading experts, explained to me, the experiment was hopelessly contaminated. The nests of bumblebees which were meant to function as a pesticide-free control group were exposed to similar levels of neonicotinoids as those in the experimental group. The government "might have been wise to abandon the trial. However, instead they chose to 'publish' it by putting it on the internet – not by sending it to a peer-reviewed journal. This is not how science proceeds."

What this illustrates is that these trials have taken place far too late: after the toxins have already been widely deployed. The use of neonicotinoids across Europe was approved before we knew what their impacts might be.

Experiments in laboratory or "semi-field" conditions, free from contamination, suggest that these toxins could be a reason for the rapid reduction in bee populations. We still know almost nothing about their impacts on other insect pollinators, such as hoverflies, butterflies, moths, beetles and midges, many of which are also declining swiftly.

Walport went on to suggest that the proposed ban would cause "severe reductions in yields to struggling European farmers and economies". Again, this is simply incorrect: in its exhaustive investigation, published last month, the House of Commons environmental audit committee concluded that "neonicotinoid pesticides are not fundamental to the general economic or agricultural viability of UK farming". In fact they can prevent a more precise and rational use of pesticides, known as integrated pest management. The committee reports that all the rape seed on sale in this country, for example, is pre-treated with neonicotinoids, so farmers have no choice but to use them, whether or not they are required.

He then deployed the kind of groundless moral blackmail frequently used by industry-funded astroturf campaigns. "The control of malaria, dengue and other important diseases also depends on the control of insect vectors." Yes, it does in many cases, but this has nothing to do with the issue he was discussing: a partial ban on neonicotinoids in European crops. This old canard (if you don't approve this pesticide for growing oilseed rape in Europe, children in Mozambique will die of malaria) reminds us that those opposed to measures which protect the natural world are often far worse scaremongers than environmentalists can be. How often have you heard people claim that "if the greens get their way, we'll go back to living in caves" or "if carbon taxes are approved, the economy will collapse"?

But perhaps most revealing is Walport's misunderstanding of the precautionary principle. This, he says, "just means working out and balancing in advance all the risks and benefits of action or inaction, and to make a proportionate response". No it doesn't. The Rio declaration, signed by the UK and 171 other states, defines it as follows: "Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation." This, as it happens, is the opposite of what his article sought to do. Yet an understanding of the precautionary principle is fundamental to Walport's role.

Among the official duties of the chief scientist is "to ensure that the scientific method, risk and uncertainty are understood by the public". Less than a month into the job, Sir Mark Walport has misinformed the public about the scientific method, risk and uncertainty. He has made groundless, unscientific and emotionally manipulative claims. He has indulged in scaremongering and wild exaggeration in support of the government's position.

In defending science against political pressure, he is, in other words, as much use as a suit of paper armour. For this reason, he'll doubtless remain in post, and end his career with a peerage. The rest of us will carry the cost of his preferment.

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