ITV chief exec Michael Grade has appointed legal media firm Olswang to investigate events surrounding the upcoming documentary Malcolm and Barbara: Love's Farewell.

The broadcaster found itself at the centre of a row over pre-publicity for the show, which had claimed that the programme would feature the moment that the subject - Alzheimer's sufferer Malcolm Pointon - passed away.

The footage actually depicted Pointon's lapse into a coma before his death some three days later. Today filmmaker Paul Watson insisted that he had raised concerns with ITV but accused the broadcaster of making him a "scapegoat" by not responding speedily.

Grade, who has previously declared that he would take a "zero tolerance" approach to viewer deception, said the investigation would be "thorough, but speedy".

"We need to discover why the film was originally understood to include the moment of death only for it to be established, after the intervention of Malcolm Pointon's brother Graham earlier this week, that he died some days after the last scene in the film," he explained.

"I intend to establish the facts in this case as quickly as possible. I will publish the conclusions of the report and then take effective action as necessary."