Wildlife bosses say a drone operator disturbed 1,000 protected grey seals by flying just “a few feet” above them.
They are calling for tougher action against anyone who illegally harasses the colony on the Ythan estuary at Forvie, Aberdeenshire.
The site has been designated a protected zone for the sea mammal since May 2017 and it is an offence to harass the seals but no-one has yet been charged with harassment.
Police are investigating claims that a man was captured on camera using an aerial drone to film the colony of 1,000 grey seals who live on the Ythan estuary at Forvie, whilst others walked on the beach next to the animals.
Ythan Seal Watch, which monitors the site, has again repeated calls for the seals to be better protected after incidents last year led to stampedes – and wants a better fence to be installed to warn off would-be harassers.
It has called on the government agency Marine Scotland and Scottish Natural Heritage (SNH) to step up pressure on people breaking the rules, who could face six months in prison or a £5,000 fine.
Group spokesman Lee Watson volunteers his free time to monitor the estuary and has catalogued scores of videos of visitors ignoring signs and fences and entering the seals’ protected area on the north side of the estuary.
Last weekend he says he saw a man on camera who was operating a camera drone just “a few feet” above the seals.
Mr Watson said: “I would like a clearly defined fence to be erected on the edge of the designated site to make it absolutely clear people should not be there – that way they cannot claim ignorance.
“But no-one seems to want to build it.
“By the time a person gets to the seals – they have walked past at least two or three warning signs – but they clearly are not working.”
In a statement released last month, SNH reminded people not to get too close to the sealsand directed people who wanted to see them to the Newburgh beach to view them from a safe distance.
Annabel Drysdale, SNH’s Forvie nature reserve manager, said: “From there, you can enjoy the best views and won’t risk disturbing them while they haul out.
“We all love to watch wildlife, but we also need to protect it. If you come across seals on the beach, stay at least 150 metres away and if one or two heads come up, that means you’re close enough.”