A businessman whose revolutionary water-saving toilet flushing system is up for a major prize has accused public and private organisations of apathy after repeatedly snubbing his invention.

David Wilks's innovative Interflush system is a simple add-on piece of equipment costing £17.95 which enables 90 per cent of toilets to have a variable flush.

Mr Wilks, who runs VaryFlush Ltd, has spent a decade developing the device which he claims can save the average household £100 a year or 26,000 litres of water a year.

He said if it were fitted universally in the UK it would save the equivalent of half a billion litres a year - twice the equivalent of Europe's biggest reservoir, the Kielder Dam.

His award-winning device could pick up another prize at next week's British Invention Show at Alexandra Palace in London.

But despite a growing need to conserve water there has been little or no enthusiasm from toilet manufacturers, DIY stores and public bodies despite prolonged marketing efforts.

Mr Wilks, of Mirfield, has sold about 3,000 of the kits mainly from his website or through conservation organisations such as the Centre for Alternative Technology, Greenpeace and Friends of the Earth.

Although he has sold it to the Sheffield-based Northern Counties Housing Association, Mr Wilks said he had been unable to interest Bradford Community Housing Trust (BCHT).

"I've had two or three meetings with BCHT but they said it was too difficult to fit and too much trouble," said Mr Wilks. "Every world changing ideas has always had to face ridicule and not one was welcomed with open arms."

Despite repeated rejection Mr Wilks said he hoped sales would build to about a million a year.

He revealed he would be making an appearance on the BBC Dragon's Den programme next month and although no investment had been offered, he said the invention's exposure to viewers would stimulate sales.

A spokesman for BCHT said: "We were given a demonstration of the product which comes in kit form but we are moving away from siphon units and introducing water-saving dual flush valves in line with trends in the market.

"These ready-to-fit units are produced by a local firm and are being fitted to more than 1,500 homes a year as part of our modernisation programme."