The Alliance for National Parks Cymru, which includes a number of conservation bodies, said it risks diminishing their international standing.
The Future Landscapes Wales (FLW) report has been produced by a group under the chairmanship of Lord Elis-Thomas, who refused to comment.
The Welsh Government said discussions were ongoing on the final report.
The RSPB and Welsh Wildlife Trusts (WWT) said they could not support the report in its current form.
Both bodies said there was much to support in the document, but added "we must convey how disappointed we are by the report".
The FLW working group was set up by the Welsh Government in 2015.
The RSPB and WWT said the report contained no clear proposals, and displayed a lack of acknowledgement on the urgent need to address the loss of biodiversity within protected landscapes.
The report - which was due to be published a fortnight ago but will now be unveiled at a later date - was seen by BBC Wales' Newyddion 9.
It states that "its desire is to unlock the full potential of all landscapes in Wales" and national parks and areas of outstanding natural beauty have a pivotal role to play in the future prosperity of the country.
It calls on more collaboration to create employment opportunities and says "communities need to be inspired to develop their own vision and long-term goals for the future to generate employment and create opportunities for young people to stay in and return to their communities".
But conservationists said they were concerned the report makes no mention of the "Sandford Principle" which states the main statutory purpose of national parks is to conserve and enhance the natural beauty, wildlife and cultural heritage of the area.
A Welsh Government spokesman said: "It is important to remember this is a draft version of the report.
"The Future Landscapes Wales Programme has been highly collaborative in nature and has involved a wide range of partners, who have contributed to the discussions and the drafting.
"These discussions are ongoing as a final report is prepared for publication before the summer recess."

Crispr-Cas9 replaces harmful DNA with new code that kills cancerous cells while leaving healthy ones unharmed.
Mice with the reprogrammed code developed tumours that were much smaller than cancers in mice that did not get this treatment.
Experts call the study, in Nature Methods, promising but say it is unclear yet whether the technique would work in humans.
Dr Weiren Huang, from the First Affiliated Hospital of Shenzhen University, in China, and colleagues used Crispr-Cas9 to reprogram a cell-signalling pathway that would normally feed tumour growth in mice.
How gene editing works
Gene editing: A game-changer
Crispr-Cas9 is a DNA cutting and pasting system scientists have borrowed from nature.
Bacteria use it to protect themselves against foreign DNA from viruses.
Scientists have already begun using it in the lab to target and cut out faulty DNA in human cells that cause illnesses.
But it is not without risks.
While effective, the editing process is less than perfect and can cut out too much DNA.
These unwanted or "off-target" edits could alter other important genes, inadvertently triggering cancer, for example.
Dr Chris Lord, a gene expert at the Institute of Cancer Research, said: ""The key to translating this technique into the clinic will be to see how specific to the tumour cell the Crispr activation will be and how specific, in terms of genes, the Crispr-mediated gene cutting will be.
"These are essentially the same two issues you have with all cancer treatments - how specific for the tumour cell and how specific for the target."

Adelie Ireland, which took over The Bite Group last year, has now gone into administration.
The company based in the Lackaboy Industrial Estate makes sandwiches and snack foods for convenience stores and retail outlets.
Staff were  sent home after being informed of the news on Friday.
Administrators are examining the options for the future of the business.
A draft report on the future of the Welsh national parks has been criticised by conservationists.
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Scientists have used a gene-editing tool to stunt tumour growth in mice.
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About 80 jobs are at risk at a food manufacturer and distributor in Enniskillen.