How 'assassin' row flared up

The so-called "assassin in high heels" was threatened with the sack after raising concerns about Betsy Duncan Smith,

Aide Vanessa Gearson was told by former Tory chairman Theresa May to "bite her tongue" or she might "end up without a job", according to her evidence to the inquiry.

She also revealed that Iain Duncan Smith ordered Tory officials to wipe out all trace of a key email in which she questioned payments to the leader's wife.

Saying the Tory leader "became very angry" at her email, she added: "He advised me he had already instructed the IT department at CCO to expunge the email from the central server."

In his own evidence to Sir Philip Mawer, Mr Duncan Smith claimed that Ms Gearson's own explanation as to why she sent the email "beggars belief".

He claimed she appeared "in awe" of Mark MacGregor, then the Tory chief executive.

The email, warning of a potential "Crick style investigation" into Mrs Duncan Smith's salary, was sent to senior Tories including Mr MacGregor. It was later leaked to BBC reporter Michael Crick.