A high-profile spat involving an MP, his constituent and the police will be discussed before MPs today.
The Privileges Committee will hear from both Tory MP Tim Loughton and Sussex Police Chief Constable Martin Richards after the politician complained about being issued with a harassment warning.
Former education minister Mr Loughton originally complained about a constituent in his seat of East Worthing and Shoreham as a "nightmare".
The MP said resident Kieran Francis had serially abused him and his staff, including calling the politician a ''f****** Nazi'' and an ''arrogant, racist, lying a*******''.
But when Mr Loughton responded in an email describing his Romany Gypsy constituent as unkempt and talking ''self-serving b******s'', Sussex Police began an investigation which involved the MP being interviewed under caution.
Police spent six months investigating the MP for potential racism.
Speaking in the Commons in March last year, and using Parliamentary privilege which acts as a safety net for defamation, Mr Loughton described how Mr Francis, from Shoreham, was a ''serial complainer with more chips on his shoulder than McCain'' but ''when he doesn't get his way he becomes abusive''.
Mr Francis complained to the MP after he was described in an internal Adur District Council document as ''unkempt''.
Mr Loughton said: ''I investigated and then sent an email back to my constituent saying that, given the dictionary definition of unkempt is 'untrimmed, dishevelled and rough' the council's description - not mine - struck me as eminently accurate. Anyone who has seen a photograph of the pony-tailed, shaggily bearded Mr Francis could not but concur.
''For good measure, and uniquely in almost 16 years of being a constituency MP but probably unwisely, I let my true feelings get the better of me and referred to Mr Francis' latest whinges as 'self-serving nonsense' except the word I used in place of nonsense, the word I took off Mr Francis' own blog ... was b******s.''
MPs referred the matter to the Privileges Committee for investigation.