The UK's Cinema Exhibitors Association (CEA) has called on members to boycott Revolver Entertainment's planned Boxing Day release of Mum & Dad simultaneously on theatrical, DVD and online platforms.

In a letter leaked to ScreenDaily, CEA chief executive Phil Clapp says that while the film was 'clearly only of at best minor importance' it was still an unacceptable breach of a 'point of principle.'

The letter said any attempt to break the 17-week window between theatrical and other releases which remains at the moment the norm, was taken very seriously and called on members not to show the film.

Speaking to ScreenDaily, Clapp said members felt it remained necessary to their businesses to fight the further erosion of windows. That principle remained even if the film itself had no ambitions to become a major cinema release.

'This may be an experiment but it is not an experiment we want to be part of.'

Revolver managing director Justin Marciano told Screen last week that the move was more than just an attempt to court controversy.

The release of Steven Sheil's film - backed by Film London's Microwave digital production scheme - was an attempt to mobilise an audience which would mostly watch the film online.

The planned 15-screen theatrical release was a small but important additional way to reach further audiences and made business sense, said Marciano.

'I'm not suggesting Tropic Thunder should open day and date but for a pure indie effort that knows its market, this makes sense.'