A bitter family feud is hindering the organisers of T in the Park from resolving a bizarre problem with rare osprey birds which threatens the future of the iconic Scottish music festival.

The story began when DF Concerts, which runs T in the Park, struck a deal to use Strathallan estate, owned by the Roberts family for more than a century.

The proposed festival site is owned by Anna Roberts, who will be able to cash in if the festival goes ahead in July.

But the Sunday Herald has learned that an area known as Andrews Woods, owned by Anna's sister, is out of bounds to DF Concerts, despite several offers of cash for access.

This means ornithologists employed by festival organisers have been prevented from removing a nest used by rare ospreys - a protected species. Last week, the birds left a specially constructed new nest further away from the festival site and returned to Andrews Woods.

The Royal Society for the Protection of Birds (RSPB) has now declared the nest active and wildlife legislation prevents the ospreys from being disturbed.

A source close to the Roberts family said: "The person who owns Andrews Woods is the sister of Anna Roberts who owns Strathallan estate. Anna inherited the estate and the capital so they don't get on.

"The owner of Andrews Woods was offered a deal which would have allowed ornithologists to step on to the land and take the old nest down.

"DF tried for a very long time but the owner wouldn't take the deal. At the very heart of this is a family feud. It has nothing to do with birds."

Festival organisers must meet strict conditions imposed by the RSPB if the event is to go ahead.

But a spokesman for the charity insisted it supported the festival in principal and the plans to relocate the birds.

He said: "The problems the organisers have is not with us but with the landowners. The main owners of Strathallan estate came to a deal with DF concerts.

"There is another owner of the land where the ospreys are and they refuse to allow the old nest to be removed. As a result the ospreys have ignored the new nest and returned to the old nest.

"It is near the boundary of the main arena and it is protected legally because it is active. It is now an offence to disturb the nest.

"These birds are considerably rare. There are only 200 in Scotland, and they have to be protected.

"We are working with DF Concerts to see if we can help in any way we can. But the fact they are in the situation is unfortunate and it could have been avoided if they were able to remove the old nest."

Chief executive of DF Concerts, Geoff Ellis, suggested yesterday the future of T in the Park could be in doubt.

During a debate with Charles Dundas of the Woodland Trust Scotland, who has objected to plans to hold the event at Strathallan, Ellis said: "I don't think there is a venue, without going very far north in Scotland, which would be viable for T in the Park, so yes, I don't think it would carry on if we didn't host it at Strathallan this year."

Speaking to the Sunday Herald yesterday, Ellis appeared to roll back on his comments: "The point I was making was that, by the logic of the Woodland Trust, if T in the Park can't work at Strathallan then how could it work anywhere in rural Scotland?" Ellis also insisted the ospreys at Andrews Woods could yet choose to move to the new nest.

He said: "We're in the middle of a live planning process and when the final location of the ospreys becomes clear, we will work with the relevant organisations on the development of our plans to agree an appropriate buffer zone and manage it accordingly."

He added: "Aside from this, our planning application and environmental statement answers all questions posed by the statutory consultees and we remain confident that we can ensure the long-term protection of wildlife as well as the future of the event at Strathallan."

The Sunday Herald contacted a spokeswoman for the Roberts family but she declined to comment. We also contacted a spokesman for the Woodland Trust but he did not respond.