An unseen drama by Dennis Potter, regarded by many as the greatest television writer ever, has been relegated by the BBC to its digital channel, BBC4, where its audience is unlikely to number more than 200,000.

In buying the rights to White Clouds, a script Potter completed in the months before his death in 1994, the BBC seemed to have scored a coup. But, in a move that will stun admirers of the writer, the film will be screened in the autumn on BBC4, where at best it will attract an audience in the hundreds of thousands and at worst just a few thousand.

In a further snub to a dramatist always associated with high production values, the BBC is giving the broadcast a decidedly low-budget treatment. The actors will not wear costumes, there will be few props, and photographs will be used to convey scenery.

The BBC will not reveal the budget but it is thought to be one of the smallest for a drama by a leading writer for years.

The downgrading of the nation's most renowned TV writer is in sharp contrast to the screening of the last two linked screenplays he wrote, Karaoke and Cold Lazarus, in 1996. After Potter's death, the BBC and Channel 4 entered into an exceptional agreement to show one on BBC1 and the other on Channel 4. Potter wrote 10 pages a day of his last scripts until shortly before his death.