The sacking of David Nutt for insisting on the probity of scientific evidence that did not correspond to political exigencies has a significance well beyond the drugs debate. The essence of democracy is evidence- based argument, reason and genuine deliberation. Of course there will be a passionate clash of values and priorities, but if we cannot accept the facts we descend into a shouting match between rival prejudices.

This is not the first time the government has shown its unwillingness to accept the primacy of science in the debate over drugs. Last year its own Advisory Council on the Misuse of Drugs (ACMD) recommended – on a vote of 20-3 – that cannabis should remain a class C drug. Gordon Brown chose to dismiss the science and ordered cannabis to be upgraded to a Class B drug.

Where was the rational argument in this decision? There wasn't one. Jacqui Smith, the then home secretary, admitted at the time of the announcement to the Commons that she was taking into account "public perceptions" alongside other factors. Science and rational thought lost out to the court of what the government deemed was popular opinion.

Now they've done it again. As Professor Nutt argues , the ACMD has been systematically undermined by government. Why summon scientists to have an input to a debate where complex issues such as pharmacology and toxicology need to be elucidated, only to reject them out of hand?

Nutt dared to argue there is not the scientific backing to support labelling the drugs the government wants to label as dangerous. Even at its zenith, New Labour was never a courageous political formation; now, limping towards a general election, it is determined not to appear liberal or soft on drugs for fear it will be torn apart by foes in the press. Nutt did not get the politics and did not help his case with some ill-judged interventions. But to pay with his job is extreme.

Any successor will ponder long and hard, as many scientists are reported to be doing, about whether any scientific advice they offer will be acted on if it does not suit the political mood. What a long way we've come since Labour's ascent to power, when it promised to develop policy on the basis of evidence, not political expediency, where science would be at the heart of the debates and always be a source of rational decision-making.

Nutt's sacking would be serious enough if it was just one incident, but British politics – and our culture – is increasingly being disfigured by politicians bowing to prejudice. Sharon Shoesmith was summarily sacked as director of Haringey Social Services over the Baby P scandal. She was accountable for dreadful omissions by her department, but there was not even a nod to due process or natural law. The press demanded a head. One was offered.

Britain is losing its way, unmoored from its tradition of fair play, debate and respect for facts. Nutt's sacking was another milestone in Britain's progression from a great Enlightenment country into a place where prejudice reigns. Big Media has played its part, but so have timid, callow politicians. The dismissal demonstrates how profoundly disfigured our politics is becoming by a political class unwilling to stand up to the way public opinion is being manipulated.