It is widely believed that the quango will no longer issue planning statements when schemes are proposed.
But a statement issued by the authority said it remains committed to protecting its parks from 'overly intrusive or insensitive development'.
The RPA has been one of the most militantly anti-skyscraper organisations in the capital, commissioning studies showing how tall buildings will affect views from green areas such as Richmond Park and Hyde Park.
But sources have told the AJ that this long-standing policy has been overturned because decision makers routinely ignored planning advice, with a number of towers winning planning permission despite opposition from the RPA.
'The leadership has decided against getting involved in any significant way in planning issues,' the source said.
'They've looked at the results they've been getting and realised there's probably better ways of spending their money. It's simply a matter of resources.'
The RPA refused to officially confirm that there has been a policy about-turn.
The RPA statement said: 'The Royal Parks Agency has engaged in the public debate over tall buildings in London and their effect on views and sight lines from within the royal parks.
'We remain committed to protecting all the Royal parks in our care from overly intrusive or insensitive development that compromises the visual appeal, ambience and public enjoyment of these unique green spaces.
'We consider each planning application individually, looking at them entirely in context and in terms of their relative merits.'