The Loch Lomond and Trossachs National Park authority has been accused of a “cover-up” over the resignation of one of its leading members for failing to declare shares in a £200 million gold mining company for more than two years.

Internal documents seen by the Sunday Herald reveal that Owen McKee resigned as vice-convener and chair of the planning committee in December. This followed his admission that he had bought over half a million shares for close to £12,000 in Scotgold, an Australian company planning to dig for gold under a hill at Cononish near Tyndrum in the national park.

After “serious concern” from fellow board members about the “reputational risks” to the park, he decided to sell his shares hours before a meeting due to discuss arrangements for considering the gold mine. He remains a member of the park board and planning committee.

Board members were repeatedly warned to keep what had happened secret, and were not given the full report of an internal investigation into McKee’s shareholdings. “This matter is highly sensitive and confidential and is not in the public domain”, they were told by park convener, Linda McKay, in December.

Outdoor campaigners allege that the park authority deliberately tried to hide the reasons for McKee’s resignation from the public, and have lodged a complaint with the ethical standards watchdog. The authority is “not fit for purpose”, its leaders should be suspended and a government investigation launched, they say.

The former environment minister and SNP MSP for Argyll and Bute, Michael Russell, suggested that McKee should stand down as a member of the park board. “You need absolute transparency in matters of planning,” he told the Sunday Herald.

“This was a highly sensitive application. Mr McKee should consider his position as a member of the board and the park should publish everything it has on this.”

The park authority accepts that McKee made “a serious error of judgement” for which he had “personally paid a heavy price”. But it stresses that no planning decisions were compromised as a result of his shareholding.

After heated controversy, Scotgold was granted planning permission by the Loch Lomond park authority to mine at Cononish in February 2012. The company’s consent was amended to allow longer working hours in February this year, and it is expected to start digging soon for a claimed £200 million worth of gold.

McKee, a 77-year-old retired Lochearnhead shopkeeper and banker, has been elected four times by the local community as a member of the park authority since it began in 2002, most recently until 2018. He started buying shares in Scotgold in May 2012 - after it was given planning permission - and by March 2014 had amassed 520,000 shares at a total cost of £11,902.35.

He attended 15 authority meetings during 2012, 2013 and 2014 at which Scotgold’s gold mine was mentioned without declaring his interest. He first indicated his shareholding to park officials in October 2014, which led to his resignation from senior positions on 12 December and the launch of an internal investigation.

In an email to senior officials on 14 December, park convener McKay wrote that board members had expressed “serious concern” about McKee’s judgement. She had discussed this “loss of confidence” with McKee “along with the reputational risks to the authority, given the strength of public feeling around the Scotgold planning application,” she said.

The internal investigation report, completed in January 2015, concluded that McKee should have included his shares on his public register of interest. He should also have declared his interest at each meeting at which the gold mine was referenced or discussed, it said.

?But it added that the authority had followed the proper process. “There is no evidence to suggest that Owen McKee's shareholding in Scotgold affected any decisions made,” the report said, adding that the risk of a legal challenge was therefore “minimal”.

The story of McKee’s gold shares has been revealed by documents released by the park under freedom of information law. The documents were obtained by the mountaineering campaigner, Nick Kempe, who has been opposing the park’s plan to ban camping without permission.

The Sunday Herald reported in June that Kempe had made a complaint to Bill Thomson, the Commissioner for Ethical Standards in Public Life in Scotland, about the failure of three board members to declare an interest in the camping ban, including McKee and McKay. He has now filed a second complaint over the handling of McKee’s shareholdings.

“It is now obvious that the primary focus of park board members is looking after their own personal interests rather than the public interest,” he said. “The board is no longer fit for purpose.”

Dave Morris, the former director of Ramblers Scotland, accused the park of trying to “cover-up” the share purchases. “Those responsible should be suspended from duty while their conduct is examined,” he said.

“From gold mines to camping byelaws this national park has completely lost its way. Nobody can have any confidence in its decisions and the Scottish Government needs to order an independent investigation.”

McKee declined to comment, though he is said to be “mortified”. A former board member who knows him, local farmer Kate Sankey, thought his mistake should not be a slur on his character. “He has put his life and soul into the Loch Lomond park but did something foolish,” she said.

The park’s chief executive, Gordon Watson, stressed that a thorough investigation had concluded that no planning decisions on the mine had been taken during the period of McKee’s shareholding. “The authority still viewed it as a serious and significant error on his part not to declare his shareholding,” he said.

Watson pointed out that McKee had sold his shares “at a considerable loss”, reckoned to be over £9,500. His annual income from the park has also been halved to £7,176.60 because of the positions he had resigned.

Watson added: “This was a serious error of judgement on the part of someone who has made a very positive contribution to the park over many years and one for which he has personally paid a heavy price. However the investigation report is clear the park authority has at all times followed proper process and no planning decisions were compromised as a consequence of Mr McKee’s shareholding in Scotgold.”

The Scottish Government said it would not be appropriate to comment because a complaint had been made to the Commissioner for Ethical Standards in Public Life in Scotland.