The Mary Whitehouse Story, shown on BBC 2, told how the nationally famous TV campaigner annoyed the Beeb's director general so much that he commissioned a portrait of her with five boobs from Isherwood.

It was Sir Hugh Carleton Greene's way of "getting his own back" against Mrs Whitehouse whose tirades against BBC programmes made his life a misery.

The TV film showed a toned-down "mock-up" of the portrait by another artist.

In fact, Greene's original painting was readily available to the film-makers and would have added great authenticity to the show.

The outrageous portrait hung in Greene's office at Broadcasting House and his habit was to fling chewed pieces of paper at it – aiming to get "five out of five".

The artist's sister-in-law Molly Isherwood said: "It's a pity they didn't make a few inquiries and I would have arranged for them to have an original of the Whitehouse painting.

"My brother-in-law hated any kind of censorship and loathed Mary Whitehouse in particular. He must have been delighted when Sir Hugh commissioned the work of art.

"Although Mrs Whitehouse with five bosoms is not to everyone's artistic taste, it is a superbly competent work and very funny to many people. I can readily understand why it upsets others of a more sensitive nature."

Sir Hugh Carleton Greene's portrait of Mrs Whitehouse by Isherwood came up for sale at a little known auction house in the south of England last year and was bought by Isherwood enthusiast Steve Eckersley, of Leigh, who is just finishing a book on the controversial and now much sought after Wigan painter.

At the time, Steve said: "The Mary Whitehouse portrait is marvellous example of his work and received massive publicity in the 70s when news leaked out that Mr Greene had bought it. It will certainly feature in my book."