Media correspondent Torin Douglas reports on the findings

The award-winning programme, broadcast in October 1996, claimed to show evidence of a new heroin-trafficking route from Columbia to the UK.

Prompted by allegations in The Guardian newspaper, Carlton began an investigation with a panel including the company's broadcasting director, Nigel Walmsley.

The panel cleared Carlton executives of any intention to mislead and found the company had appropriate checking procedures for its factual programmes.

However, it said these had not been applied with "sufficient rigour" on this occasion.

The balance of evidence was that three supposed drug traffickers portrayed in the programme were acting, but independent producer Marc de Beaufort did not necessarily know this, the report said.

Nevertheless he was "complicit in falsehoods" in two cases - by presenting two parts of the drug mule's journey from Columbia to Britain as one, and by saying an interview with a "Cali cartel" member was conducted in a secret location when it was actually held in his hotel room.

The panel said: "Documentary programme makers need carefully to review some habits of their trade if television documentaries are to continue to be a service to and trusted by the public."

Findings 'will be implemented'

Mr Walmsley said: "Carlton accepts the panel's findings.

"The recommendations made by the panel are designed to sustain good factual programme making and will be implemented immediately and in full."

Television regulators the Independent Television Commission will consider the report at their next meeting on 17 December.

An ITC spokesman said: "The information received by the ITC points clearly to the fact that the programme was, in important respects, in breach of the ITC's programme code."

They could impose a statutory sanction, such as an on-screen statement or fine.

The Guardian's editor, Alan Rusbridger, said: "The panel has identified nearly 20 important deceptions in an hour-long programme which won eight awards and was shown in 14 countries.