The report, comes at a time when about 17 million people in England and Northern Ireland are still under hosepipe bans or tougher water restrictions in the wake of the drought.
The National Rivers Authority said water use could be cut, economically, by up to one-quarter. Its report, Saving Water, said changing older lavatory cisterns and extending water metering selectively were also needed to achieve the reduction. Taken together, this would drastically reduce the frequency of water shortages and the need for new reservoirs and boreholes.
The report advocates that the Government should set a maximum limit for all new washing machines of 80 litres per wash, and that all pre-1981 cisterns in households should be replaced with dual-flush versions.
These allow the option of using just five litres - half the amount of water in a conventional cistern - to flush away urine. The authority says such arrangements should be man-datory for all new homes, and that water companies could give grants to householders for the cost of replacing cisterns which it puts at pounds 30 per lavatory.
The report also suggests that all water companies should reduce their leakage rates to six litres per household per hour - equivalent to about 18 per cent of total water pumped into the mains being lost.
Most of the big 10 water companies of England and Wales have leakage rates well above that, with North West, Welsh and Yorkshire the worst offenders. The Government and the industry's economic watchdog, Ofwat, are opposed to compulsory leakage targets for the companies but the NRA has now made a clear call for them.
The authority says these three moves - on washing machines, leakage and lavatories - would together save 3.6 billion litres a day in England and Wales, 20 per cent of current consumption.
The report says installing water meters in every home would not be a cost effective way of curbing use, but it does come out firmly in favour of a gradual spread of metering ''with appropriate safeguards for low- income families.''
The priorities should be to install meters in all new homes and where mains and service pipes are being refurbished, to make the installation of meters an attractive option to customers and to concentrate on areas where water was most likely to be in short supply.
This summer's water shortages were caused in part by high use of garden sprinklers and hoses. The NRA said that if these households had had meters the problems would have been less severe. ''That is something that should be taken very seriously by the water companies,'' said the NRA's water demand chief Peter Herbertson.
Earlier this week, North West Water was granted powers to ban non-essential use of water such as car washing and watering of sports grounds. In mid- Ulster, several hundred homes have been experiencing rota cuts for the past three months, with water supplies shut off overnight for eight hours in every 24 to conserve supplies.Reuse content