The BBC's Nick Higham: "Crucial scenes were faked"

In the film Too Much Too Young: Chickens, rent boys in Glasgow were shown negotiating sex with three 'clients'.

The 'clients' were later identified as members of the documentary's production team, after allegations of faking were made on Radio 5 Live's Parris On TV programme last November.

Independent producer Maire Devine was banned from working for Channel 4 after admitting that the scenes were faked, but the channel still faces investigation by the Independent Television Commission and a possible fine.

£2m fine

It is the latest in a series of high-profile documentary faking scandals.

Carlton subsidiary Central Television was fined £2m after it emerged that its much-acclaimed film about drug smugglers, The Connection, was largely faked.

More recently, Channel 4 pulled a documentary called Daddy's Girl after the father and daughter featured were found to be an unrelated couple.

A Channel 4 statement on Too Much Too Young: Chickens said: "The film contained three scenes that purported secretly to record the activities of rent boys and their clients on the streets of Glasgow.

'Very serious'

"They were in fact constructed sequences using members of the production team to act the part of the clients."

The ITC was kept informed throughout the channel's investigation into the documentary and said that it would "consider the statement ... and members of the commission will be deciding what action will be appropriate".

"We take this seriously. Viewers have a right to expect that anything they see on a factual programme has been properly vetted," an ITC statement said.

Breach of trust

Channel 4 Director of Programmes Tim Gardam said the channel's "robust" procedures could not always guard against "deliberate and organised deception".

"The way in which the scenes were set up is an unacceptable breach of trust with the audience and Channel 4," he said.

"The overwhelming majority of our documentary producers have the utmost integrity and go about their business with scrupulous care and honesty."

The channel has since implemented new guidelines on secret filming, in addition to updated guidelines on fly-on-the-wall style documentaries.