By Nick Assinder BBC News Online political correspondent

Even Ann Winterton's best friends must have known she was doomed the minute she cracked a racist joke.

The astonishing thing is that it took Iain Duncan Smith so long to do it.

The first response from the Tory leader's spokesman was to claim she had apologised and that was the end of the matter.

The fact that anyone could crack such a joke at any time, let alone in the current climate, and think they could get away with it is breathtaking

He even apparently tried to suggest it was in the same category as Home Secretary David Blunkett's highly controversial remark about asylum seekers "swamping" some schools - hardly a convincing defence bearing in mind the furore that caused.

It was not until the following day that the shadow minister was sacked.

The hesitation in dumping her has, rightly or wrongly, created an impression that Mr Duncan Smith did not immediately comprehend the offence her so-called joke would cause.

And that will play into the hands of those who believe the Tory party's campaign to rid itself of racists is more about image than fundamental beliefs.

Bad timing

The fact that anyone could crack such a joke at any time, let alone in the current climate, and think they could get away with it is breathtaking.

Firstly, it came just next door to the area where the racist BNP fed on fears over immigration to win three local council seats in last Thursday's local elections.

In France, the success of National Front leader Jean Marie Le Pen in the first round of the presidential election raised fears of a rise in fascism across the Continent.

Le Pen's victory raised fears of fascism

And, during the last general election, the Tories were themselves hit by the revelation that the father of BNP leader Nick Griffin was a local Conservative party worker.

At that time the then leader William Hague insisted there was no room for racists in the Tories.

Mr Duncan Smith said if he became leader he would take "direct, rapid and decisive" action against anyone in the party holding racist views.

Since his election, one of his key policies has been to make the Tory party more inclusive and tolerant and to root out prejudice.

Intolerant

The Tory leadership has privately accepted that there is a strain of intolerance and racism running through the party, particularly amongst older members in the constituencies.

But there is a genuine belief among the most senior party members that this is unacceptable.

They have also recognised that it is often difficult, if not impossible, to change deeply held prejudices and that often the only way to deal with them is to outlaw them.

Duncan Smith promised to stamp out racism in his party

There has always been a suspicion amongst some, however, that the moves towards tolerance were cosmetic and all about electoral considerations.

The party leadership fiercely deny this, so Ann Winterton's remarks could not have been more damaging.

Mr Duncan Smith has time and again stressed that he means what he says about creating an inclusive party where such views are simply not tolerated.

His determination has now been put to its first major test.