The BBC has crossed all kinds of lines with this bizarre stunt: Tory fury as BBC sends hecklers to bait Howard. (Hat tip: Shiplord Kirel.)

The Tories have made an official protest after the hecklers, who were given the microphones by producers, were caught at a party event in the North West last week. Guy Black, the party’s head of communications, wrote in a letter to Helen Boaden, the BBC’s director of news, that the hecklers began shouting slogans that were “distracting and clearly hostile to the Conservative Party”.

These included “Michael Howard is a liar”, “You can’t trust the Tories” and “You can only trust Tony Blair”.

Mr Black’s strongly-worded letter accused the BBC of staging the event “to generate a false news story and dramatise coverage… intended to embarrass or ridicule the leader of the Conservative Party”. The letter said that BBC staff were guilty of “serious misconduct”. At least one of the hecklers was seen again at a Tory event in the North East, Mr Black added.

Last night, the BBC claimed that the exercise was part of a “completely legitimate programme about the history and art of political heckling” and said that other parties’ meetings were being “observed”. However, The Telegraph has established that none of Tony Blair’s meetings was infiltrated or disrupted in similar fashion.