An MP has slammed police bosses for “losing the plot” after warning him he could be prosecuted for harassing a constituent who subjected the politician and his family to “vile abuse”.

Speaking in a special House of Commons debate, East Worthing and Shoreham MP Tim Loughton claimed Shoreham resident Kieran Francis had conducted a “vile crusade” against himself and colleagues since last year.

Since raising the issue in Parliament earlier this year, the Conservative MP said the “onslaught of vile abuse” had been stepped up to include a comment urging him to commit suicide, “vile, contorted accounts” of his parents’ divorce and doctored pictures of his children posted online.

But, after telling Mr Francis by letter he would no longer repre¬sent him as his MP, Mr Loughton slammed Sussex Police for warning him he could be prosecuted if he continued, as the constituent claimed the note was harassment.

The former children’s minister said the issuing of a police information notice (PIN), signed by senior officers, was a “clear breach of parliamentary privilege”.

Mr Loughton said: “The chief constable [Martin Richards] has been content to waste taxpayers’ resources on this nonsense while the senior management of his force is brought into disrepute.

He has clearly lost the plot when it comes to distinguishing between the victim and the perpetrator.”

The Conservative MP told the Commons that Sussex Police spent six months investigating him for alleged racist abuse after describing “nightmare constituent” Kieran Francis as “unkempt”.

After this, he said he took advice from a Parliament clerk and sent Mr Francis a complete Hansard record of the March 13 debate, which said he would no longer represent the constituent.

But Mr Loughton said the actions he believed would be covered by parliamentary privilege, resulted in him receiving a PIN.

In a statement, Sussex Police said the matter related to an investigation into a series of allegations and counter allegations “where all parties have in turn been considered as victims and suspects”.

A spokesman said five PINs had been issued, explaining a continuation of the behaviour would lead to re-opening of the investigation and consideration of arrest or prosecution.

Responding to the accusations, Assistant Chief Constable Robin Merrett, of Sussex Police, said by issuing the notices it had hoped to bring the issue to a conclusion.

Jemima Bland, prospective Liberal Democrat candidate for Worthing East and Shoreham, said Mr Loughton should have used half an hour of valuable parliamentary time to protest at the closure of two police stations in his constituency, rather than moan about his personal treatment by Sussex Police.

The Argus contacted Mr Francis but he did not respond.