By Nick Assinder BBC News Online political correspondent

Just as Iain Duncan Smith appeared to have escaped with one bound, he has been dealt yet another blow to his leadership.

The enforced departure of Tory chief executive and the leader's chief of staff Barry Legg is a setback Mr Duncan Smith could well have done without.

It comes just a week after the Tories won a better-than-expected local election victory, helping remove some of the doubts over Mr Duncan Smith's leadership.

But the latest development undermines some of that and represents a direct challenge to his personal authority.

Once again a personal appointee has been the source of problems for the Tory leader.

Mr Duncan Smith infuriated so-called modernisers in his party when he allegedly forced out previous incumbent Mark MacGregor and gave the job to Eurosceptic Mr Legg, a personal friend.

The decision sparked a bitter attack from leading moderniser and former leadership contender Michael Portillo.

Now Mr Duncan Smith has been forced to get rid of his own man amid suggestions that he had flouted internal rules.

It is being suggested that it should have been up to the party's board to at least approve the appointment, if not make it in the first place.

The board is due to meet next week and the decision is clearly designed to see off a more embarrassing blow when it was expected to abolish the post then anyway.

Tory sleaze

But what will be particularly damaging for Mr Duncan Smith is the fact that, rightly or wrongly, this episode will remind voters of the sleaze the party has tried to put behind it.

The Westminster council homes for votes row hit the Tory party badly more than two decades ago and his sacking revives all those memories.

It also proves that the in-fighting between the so-called "mods" and traditionalist "rockers" in the party is far from over.

However, it was being suggested that Mr Duncan Smith now felt that, thanks to his local election success, he was in a more powerful position to clear the air.

And many in Central Office now hope this will allow them to put the in-fighting behind them.

The move against Mr Legg was also taken on the same night that Tony Blair saw off a minor rebellion over foundation hospitals - presumably in an attempt to bury it.

But it seems certain to once again raise fresh doubts over Mr Duncan Smith's judgement and leadership.

Once again, the troubles buffeting the Tories have been self-inflicted.