Having carefully surveyed 139 beaches last August, the height of the holiday season, the group sees unmistakable signs of improvement.
Its inspectors graded beaches as A, B, C or D based on how well they scored in access, cleanliness and litter control on shore, safety in the water, control of dogs, facilities and recreation, maintenance and public information. Grades C and D were deemed "unsatisfactory".
A grade A was given to 41 beaches, of which Bournemouth's are the most popular. Brighton was a B and Blackpool's north and south beaches were Cs.
Eleven resorts - 8 per cent - were assessed as grade D, including Southport on Merseyside. East Anglia had the cleanest beaches and the most improved ones, while the North-west was the region with the worst. None of its beaches had a grade A.
Trevor Dickson, who headed the survey, said it showed a big improvement on 1995. Ten more resorts had achieved a grade A and two-thirds of all the beaches inspected were either in that category or grade B.
''We're encouraged,'' he said. ''We feel the findings of earlier surveys have been well received by the local councils responsible for the beaches and we can now see a real improvement.''
The survey did not cover the amount of sewage pollution in the bathing water - although to score well resorts had to provide prominent notice boards giving this information to the public.
The Government released the latest figures on sewage pollution a few weeks ago. They showed that in 1996 89.6 per cent of Britain's 472 designated bathing waters met the minimum, mandatory European Union standard - a minuscule improvement on the 89.0 per cent pass rate in 1995.
The tiny increase disappointed the water industry and the Government, because since privatisation about pounds 2bn has been sent on coastal sewage schemes, largely to comply with an EU directive setting maximum sewage bacteria levels. The water companies now say there are other sources of sewage pollution such as buildings with their own sewage outfalls and farms.
Blackpool central and north beaches met the EU's basic standard for the first time this year, thanks to a pounds 150m improvement scheme. But the resort's south beach still failed.
Mr Dickson said sewage pollution in water had been given undue weight over the cleanliness and good management of beaches on shore. ''Our surveys find that the great majority of people go to the beach to sunbathe, enjoy the fresh air and views and to walk, not to go in the water,'' he said.
Nonetheless, 31 United Kingdom beaches had now been awarded the European Blue Flag, nearly twice the number for 1995. The flag is given to beaches that are clean and well run on shore and whose water meets the most stringent EU standard.
Bathing at its best
The following 13 beaches were judged Grade A in the Tidy Britain Group's onshore survey, but they also have European Blue Flags - which means they meet the European Union's highest bathing-water quality standard.
England: Sheringham, Norfolk; Southwold, Suffolk; Sheerness Beach Street and Leysdown Grove Avenue in Kent; Bournemouth, Poole Sandbanks and Swanage Central in Dorset; Oddicombe, Devon; Sennen Cove and Porthmeor St Ives in Cornwall.
Scotland: St Andrews West Sands; Aberdour Silver Sands.
Wales: Pembrey Country Park, Tenby North.