You cannot describe Ukip as a far-right party without running into trouble. Respectable commentators tell you that, while individual members may be neo-fascists and that while Ukip had indeed allied with far-right parties in Europe, it does not come from fascist tradition. And I just about accept that.

Hardly any commentator, respectable or otherwise, notices that Nigel Farage has created his own stab-in-the-back myth. The treacherous “Westminster elite” so despised the decent people of Britain that it flooded the land with foreigners who “took our country from us”. This is the manure in which far-right movements have always grown. But, once again, if anyone objects, I accept that Farage is not a führer or duce.

Rather than arguing about labels, let us agree to allow the facts to speak for themselves. Farage is a rabble-rouser and a coward. He plays with racism, the way Ian Paisley used to play with sectarianism: whips it up, then backs off just before he can be accused of inciting violence.

He does not attend the meetings of the European parliament to defend British interests but pockets the money of the “hardworking taxpayers” he affects to represent and skips away. He claims to be a patriot while defending Britain’s enemies in the Kremlin. He claims to be the friend of the working man, while slapping down his economics spokesman for proposing tax rises that would hurt his backers in the City.

As for the men and women he leads, Ukip candidates and donors have suggested they want to drive Lenny Henry out of Britain because he is black, bar women from the boardroom and stop gays from having sex because as, everyone knows, God punishes the sin of Sodom by flooding the Thames Valley.

If you cannot call Ukip a far-right party, you can at least say that it is an alliance of the septic and the geriatric: a movement of the empty-headed led by the foul-minded.

It tells you everything about the absence of principle in the mainstream parties that they don’t even try to beat Farage. Political commentators could not have been more foolish when they believed David Cameron’s promise to “throw everything” he had at stopping Ukip winning in Rochester.

Cameron may have thrown money and marketing strategies, but he did not throw punches. The Conservative attack on Ukip’s ideas never came. Cameron, who once presented himself as a moderate, instead conceded acres of ground to the extremists, no more so than on the immigration question.

As late as March 2013, Cameron was careful to preface a speech proposing restrictions on immigration by praising “Polish heroes who fought for us during the war, West Indians who helped us to rebuild afterwards, those who’ve come to our shores seeking a safe haven from persecution”.

He understood the dangers of provoking hatred and worked to ensure that no racist party or thug, and no employer or landlord looking to exclude blacks, could find comfort in what he said. You no longer hear Cameron insist that most immigrants are good and hardworking people. He has abandoned the centre and veered to the right. The good manners he learned at Eton have deserted him on the way – and what is the point of having an old Etonian if he doesn’t know how to behave? The new Cameron wants to show Ukip voters that he is just as right wing as Farage. Even when Mark Reckless proposed the repatriation of immigrants living in Britain, the Tories did not hammer him for fear of appearing soft.

Alex Massie of the Spectator brilliantly summarised Cameron’s strategy of never allowing Farage to outflank him on the right by saying that it came down to the slogan: “Ukip are right: don’t vote for them!”

The funeral of Cameron’s gutless strategy came when a desperate prime minister appealed to the centrists among Labour, Green and Liberal Democrat supporters in Rochester to vote tactically to stop the extremist Ukip candidate winning. Reasonable people could not see the difference between the extremist Cameron and extremist Farage and ignored him.

Cameron’s capitulation carries a warning. He won’t fight Ukip not only because he is frightened of Farage but because he is a prisoner of his party’s right. If he wins the next election, we now know that he will keep capitulating because he is a leader without honour or inner strength, whose own cynicism defeats him.

Not that Ed Miliband is any better. Cameron has tried and failed to pull the political insiders’ “triangulation” trick, practised by Bill Clinton: get close to your opponent (Ukip in this case), steal his votes and victory is yours. Miliband has tried to follow the “core vote” trick of George W Bush and Barack Obama: get out Labour’s “core” – about 30% of the electorate – throw in old Lib Dems, who cannot forgive the Tory alliance, that’s another 5%, and, eureka!, our strange electoral system will deliver victory. Like a child building a house out of Lego bricks, Miliband thought he could pick up the handfuls of voters he needed for victory and forget about the rest.

A friend should have told him that astounding condescension lay at the heart of his “35% strategy”. Labour assumed that its “core” supporters would not listen to anyone else; that, even at a time of economic distress and political disintegration, Labour “owned” them.

For years now, I and others have been waiting for Miliband to launch a sustained attack on Ukip with whatever vigour the poor thing could manage. But even in this year’s European elections, he preferred to ignore a radical rightwing party, which was heading for victory, and emptied his revolver into the corpse that was once Nick Clegg. You see it was more important for Miliband to remind his Lib Dem Lego bricks that they should stick with Labour rather than fight a foul stain in national life.

Ukip will not be beaten until those in all parties, who know that most immigrants are not the scrounging scum of Ukip nightmare, say clearly that the debate must be about numbers, not race. It will not be beaten until people who believe in maintaining Britain’s place in the world accept the need for reforming the European Union, but tell the electorate that we will founder if we leave.

It most certainly will not be beaten by David Cameron and Ed Miliband, who give every appearance of believing that you can win a battle without fighting it.