The Scottish Executive is facing calls to look into the membership of a secretive, all-male Edinburgh club, after it emerged that large swathes of the Scottish legal establishment are listed as members.

The Lord Advocate, Colin Boyd, is to be forwarded an exhaustive membership list of the Speculative Society, a 250-year-old club which excludes women from its membership and which meets in candlelit vaults below Edinburgh University's Old College during the winter .

The list, taken from the 'Spec ' handbook and verified by two members, is populated by law lords, advocates, sheriffs and businessmen, and includes a former Cabinet minister, a prominent publisher and one of the country's leading bankers. It came to light after an investigation by Robbie the Pict, the Skye Bridge anti-tolls campaigner, who is to petition the parliament once it reconvenes after the summer recess.

The Spec is essentially a private debating club in which young lawyers -- ordinary members -- hone their debating skills. However, the presence on its books of so many leading figures from the fields of Scots law and commerce -- all extra-ordinary members -- raises questions about the 'old boys' network' in Scotland.

Last week, the SNP's Alex Neil alleged a similar network was responsible for the appointment of Sir Muir Russell, Scotland's top civil servant, as the new principal of Glasgow University . Russell is not a Spec member .

'Scotland is a small country but it seems to be particularly susceptible to an incestuous relationship among the powers that be,' said Neil, who is convener of the Scottish parliament's enterprise and lifelong learning committee. 'Even if there's no formal or verbal agreement, it's almost an unwritten law that you'll scratch my back and I'll scratch yours.

'It's an old boy network. Very often these people are in law, the civil service, senior banking or are senior businessmen.

'The fact there's a so-called Speculative Society, which I certainly didn't know about, suggests the network is even more formal than we had expected.'

Among the extraordinary members are the Lord Lyon and the Lord Justice General, Lord Cullen, along with Scots law lords, Lords Marnoch, Hamilton, Prosser, Milligan, Coulsfield, Maclean, Osbourne, Abernethy, Johnston and Nimmo Smith. From the House of Lords are Lords Hope, Clyde, Mackay of Clashfern, Jauncey, Keith and Cameron of Lochbroom, as well as several High Court judges, sheriffs and a host of advocates.

Others include Scottish Tory justice and home affairs spokes man Lord James Douglas-Hamilton, Iain Noble of Noble Grossart Bank, the whisky writer Charles MacLean and Peter Derby, a former Master of the Worshipful Company of Actuaries. The Duke of Edinburgh is an honorary member.

Robbie the Pict alleges the fact that so many law lords are members of the same club constitutes a breach of Article Six of the European Convention on Human Rights, which guarantees the right to 'a fair hearing by an independent and impartial tribunal'.

'Every punter has a right to know who's on that list and reflect upon what happened to them in court,' said the Pict. 'The framework exists in terms of international law and the right to a fair tribunal. They have crossed this line and violated human rights because there's a visible, plausible connection.

'If Colin Boyd has got this cabal he doesn't know about, there's something very wrong. He must investigate this.'

Professor Robert Black, of Edinburgh University, an expert on Scots law and a former Spec president, agreed there was some merit in the Pict's argument. 'I concede that there is an issue,' he said .

Chartered accountant HM Holmes, of Edinburgh, is on the list, but refused to comment. Robin Hodge, publisher of The List, did not return calls.

However, extraordinary member Humphrey Errington, producer of Lanark Blue Cheese, who successfully challenged the decision by health officials to close his dairy, laughed off the claims of an old boy network.

Errington said it was composed of 'some complete oddballs and rogues' and has 'a whole lot of completely antiquated customs', such as not recognising decimalisation and imposing fines for not attending in units of seven or eight pence.

'If I felt in any way it was a club of cronies getting together, I wouldn't have belonged to it.'

The Spec was formed in 1764 and counted Sir Walter Scott, Robert Louis Stevenson and Hugh MacDiarmid among its members. Lord James Douglas-Hamilton said he had been a member in the mid to late 1960s and early 1970s but had not attended for some 25 years.

He said: 'It is, to a large extent, an after-dinner debating society. It's a place where people learn to make polished after-dinner speeches, and that's its strength. It wasn't into current disputes.'