By Nick Assinder BBC News Online political correspondent

Make no mistake, if the row over Cherie Blair's property dealings concerned a minister there would be powerful calls for his or her resignation.

Because, whatever the rights and wrongs of the dealings between Mrs Blair and Peter Foster, someone in Downing Street is responsible for journalists being told an untruth.

The prime minister's wife may be right when she insists that, having done nothing improper, her dealings were none of the media's business.

But that was never going to stop the media asking about her relationship with the convicted conman and his role in negotiating the purchase of property in Bristol for her.

So, when those questions were asked the prime minister's official spokesman told political journalists that Mr Foster had not been involved in negotiating on Mrs Blair's behalf.

An untruth?

Indeed, Downing Street's own website on that day repeated the spokesman's insistence that "if any negotiations had taken place, they had been carried out by Mrs Blair and her lawyer".

Thanks to the publication of emails between the two people, it is now accepted that this not exactly accurate.

Challenged over the fact that he told journalists an untruth, Mr Blair's spokesman said on Thursday morning:"Did we know the detail as outlined in Mrs Blair's statement?No."

And asked whether he had been misled over the issue, he replied: "The prime minister's wife's statement speaks for itself."

Spin machine

This is serious enough for some to be asking questions over the future of civil servants in the Downing Street press machine.

If this had concerned a minister's dealings, there would be calls for a full statement in the House of Commons and for resignation.

The suspicion here will be that Mrs Blair realised her dealings with Mr Foster raised questions about her judgement, at least, and that the whole affair - no matter how innocent - would prove embarrassing.

It will also not end the questions over Mrs Blair's friends

It is possible the instant response was to give out as little detail as possible. But in doing so, a misleading account was told and not quickly corrected.

Indeed, despite persistent questioning, it was not until the e-mails were published by the Daily Mail that Downing Street changed its line.

It has now been accepted by Mrs Blair that a "misunderstanding" occured and she regrets it.

And, in a second statement, she has stressed the blame lay with her and not Downing Street press officers.

But that will not end this affair which might not have escalated to this point if the full, embarrassing truth had been told at the time - even though it was considered a private matter.

It will also not end the questions over Mrs Blair's friends.