Management at Britain's largest national park wants to increase its revenue by 50% over the next eight years.

Cairngorms National Park Authority has unveiled ambitious proposals to bolster tourist numbers by 2015.

Although no definitive projects have been announced, the authority insists the goal will be approached in a "sustainable manner". It has nevertheless led to concerns about how officials will ensure a delicate balance between tourism and conservation.

The planned revenue boost was announced yesterday as master plans, setting out the future of two of Scotland's national parks, were approved by ministers.

Blueprints charting how CNPA will progress over the next five years, along with similar plans for Loch Lomond and Trossachs National Park (LLTNPA) were approved by Sarah Boyack, Deputy Minister for Environment and Rural Development.

Though far from all-encompassing, the plans put in place a broad policy overview. Key to both is the issue of sustainable development.

Last year, CNPA reported an income of £4.63m - but £4.59m of that constituted grants from the Scottish Executive. It now intends to ensure increasing numbers of businesses and hotels seek accreditation from VisitScotland to encourage visitors.

As revealed by The Herald yesterday, LLTNPA's master plan - along with its revised byelaws, which come into force on May 21 - also found favour with the executive. Responding to increasing antisocial behaviour, its rangers will now have the legal authority to report people directly to the procurator-fiscal.

Referring to the new bye-laws, Dr Mike Cantlay, LLTNPA convener, said: "We will step up enforcement in key areas, with the introduction of our new patrol boat in April. We also hope to have the police joining our rangers on patrol again this year.

"We will do all we can to raise awareness among loch users about the changes during the lead-in period."

The announcement at Cairngorms was seen largely as good news. However, many communities around the boundaries of the park - which, at 1460sq miles, is already the largest of its kind in Britain - have been campaigning for an increase in its size south of Blair Atholl.

A private member's bill by SNP MSP John Swinney, proposing such changes, failed to gain support among his parliamentary colleagues earlier this month.

The park plan hopes to encourage old and new crofters to farm the rugged terrain around the Cairngorms; maintain its deer population with minimal deer fencing; increase the use of local food suppliers and producers; and increase the availability of rented and owned housing to meet a small projected rise in population.

David Green, CNPA convener, said: "I am delighted ministers have approved the plan. The vision is rightly ambitious and the plan has set us all targets we must achieve if we want it to become a sustainable and world-class community for its habitats, wildlife, residents and visitors.

"But this is only the beginning. The challenge now is for all of us involved in the park to deliver the plan. I hope the collaborative approach not only continues but strengthens as we now look to put it in place."

Jane Hope, CNPA chief executive, added: "This is an important milestone for the park and everyone involved in it. Our focus now must be in implementing it and making those aspirations a reality. It will be a busy five years but we are all looking forward to it."

Ms Boyack said: "I am delighted to approve the first plans for both of Scotland's national parks. This demonstrates the significant progress that has been made since the two parks were set up several years ago.

"They were established to protect the outstanding natural beauty of the areas. These plans are integral to that objective while also addressing other important issues, such as living and working in the park, tourism and outdoor recreation."