The huge events planned for Hyde Park, Kensington Gardens, Regent's Park and Horse Guards Parade "risk going far beyond what can or should be tolerated", according to the Friends of the Royal Parks.
In a further criticism of the plans, Dame Jennifer Jenkins, who chaired the Royal Parks Review, has written to Chris Smith, the Secretary of State for Culture,saying that "the character of the parks is being put at risk".
The shows, which will feature attractions such as Simply Red, Bryan Adams and Cliff Richard, are being staged by the marketing arm of the Royal Parks Agency. It is the first full season of large-scale ticketed events in the parks and will deliver about pounds 1m in profit, which will go towards maintenance and development.
Since becoming an executive agency in 1993, the eight royal parks have been required to raise revenue of their own to complement their government grant, which this year will total pounds 26.4m.
It is the scale of the forthcoming events that is bringing protests. In Hyde Park, they will begin with Capital Radio's Party in the Park for the Prince's Trust on Sunday 4 July, a concert lasting from 12.30pm until 8.45pm. at which 100,000 people are expected.
After that, a 17,500-seater arena is to be built for three more weekends of concerts in a specially fenced-off area. Cliff Richard will star in three shows on 16, 17 and 18 July; Bryan Adams will be in concert on 25 July; and Simply Red will feature in three more - on 29, 30 and 31 July.
The following month there will be three important concerts in adjoining Kensington Gardens: Chris de Burgh on 13 August; the English National Opera on 14 August; and the Royal Philharmonic Orchestra on 15 August.
In September, there will be five evenings of concerts on Horse Guards Parade, site of the Trooping the Colour.
In the annual report of the Friends of the Royal Parks Forum, published this week, Sir Alan Bailey, the chairman, says that the planned concerts represent "a new and growing threat".
He adds: "In our view frequent pop concerts and other huge events, as foreshadowed in the plans for Hyde Park and Horse Guards Parade, risk going far beyond what can or should be tolerated.
"The damage from these event to the parks' fabric (grass, flowerbeds, trees) and to their proper function as a haven of peace and quite in the middle of London, is incalculable."
But a spokesman for the agency said the parks had no choice as the funds available for restoration and maintenance were insufficient for all that needed to be done.
Simon Petherick, chairman of Royal Parks Enterprises, defended the summer season of shows. "I think there is a genuine consensus that there should be a certain number of popular events in the parks." he said. "We are making a deliberate attempt to try and be reasonable about staging events. But I can't deny I might come across some people who will say, `We just don't want it'."
EVENTS PLANNED FOR THE 1999 SUMMER SEASON
The Regent's Park
A new flower show in central London
Venue: Marylebone Green, Regent's Park
Capital FM's Party for the Prince's Trust
Concert for a 100,000 people in Hyde Park
Venue: The Parade Ground, Hyde Park
Sir Cliff Richard launches a three-weekend concert season at the 17,500- seat arena in Hyde Park
Venue: The Route of Kings, Hyde Park
Pop concert with the Canadian singer-songwriter Venue: The Route of Kings, Hyde Park
Venue: The Route of Kings, Hyde Park
The Kensington Gardens Concerts
13 August: Chris de Burgh
14 August: English National Opera
15 August: Royal Philharmonic Orchestra
Weekend of picnic concerts
Venue: Buck Hill, Kensington Gardens
The Horse Guards Parade Concerts
After 1998's successful world premiere of Mike Oldfield's Tubular Bells III, the Royal Parks will host five evenings of concerts on Horse Guards Parade. Details of the artists performing will be announced soon
Venue: Horse Guards Parade, London's largest single open space