The BBC report on Ken Livingstone really says it all:

London’s mayor knew there were financial problems with some community projects before he publicly denied it, it has been revealed.

London Development Agency (LDA) chairman Manny Lewis said he told Ken Livingstone there were “discrepancies” in some of the projects’ accounts. The mayor subsequently stated publicly that all finances could be accounted for.

If, say, a Conservative MP had been caught out in the same way do you think Labour MPs would just turn their backs and ignore it, or would they be demanding blood, resignation and 1001 other punishments?