Ian Oakley, the Conservative parliamentary candidate for Watford, has been arrested in connection with a hate campaign directed at the town's local Liberal Democrat group.

Mr Oakley, who is also a councillor for the London Borough of Hillingdon, is thought to have been arrested yesterday (Friday).

A police statement, released today (Saturday) said: “We can confirm a 31-year-old man from West Drayton was arrested on Friday, yesterday, in connection with a series of criminal damage and harassment offences, the victims of which were local members of a national political party.

“He has been given police bail pending further enquiries.”

The police investigation, called Operation Tuition, started in 2005 after several Lib Dem supporters received poison pen letters aimed at Watford councillors.

One of the victims was Mark Watkin, the Liberal Democrat councillor for Nascot ward.

The case is considered so serious Hertfordshire Constabulary's major crime task force has been investigating the matter.

As well as poison pen letters, the police operation has encompassed criminal damage to property. It is known car tyres have been slashed and bodywork damaged.

Speaking today, Mayor of Watford Dorothy Thornhill said: “We are absolutely delighted that after three years of harassment and distress somebody has finally been arrested.

“We are pleased the police have persevered with this and now it is up to the CPS to obviously carry it forward.

“We don’t want to say anything else that could jeopardise any court case but we are delighted they are proceeding with the investigation.”

Mr Oakley was selected as the Conservative candidate for Watford in November 2006. Before that he was the campaign manager for Watford in the 2005 General Election.

He is a Councillor for Northwood in the London Borough of Hillingdon. Mr Oakley was this afternoon unavailable for comment on his office number, his mobile or at his home.