The G8 leaders will gather at Gleneagles Hotel

BBC Scotland has learned that the police are to tighten security measures for the area as a precaution against rogue protestors.

Holyrood Palace and the new parliament building are seen as potential targets for possible trouble-making this July.

But the idea of the perimeter fence has been dubbed "ridiculous" by the G8 Alternative Group.

Spokeswoman Jill Hubbard said the structure, which will be up to eight feet high and made of steel mesh, was "totally over the top".

The bill for the fence, to be patrolled by scores of officers, is likely to be tens of thousands of pounds.

Edinburgh march

BBC Scotland's political correspondent, Glenn Campbell, said it was thought the reason for the move was more precautionary than in response to a specific threat.

It is understood that the Queen has dropped plans to stay at Holyrood during the summit, cancelling a summer garden party as a consequence.

The G8 summit takes place between 6 July and 8 July

Edinburgh is likely to be the focus for anti-capitalist protests as world leaders prepare to meet at the Perthshire summit between 6 July and 8 July.

Upwards of 100,000 people are expected at a Make Poverty History march in the capital on 2 July.

SNP deputy leader Nicola Sturgeon told the BBC's Politics Show that the move "may be a bit of an over-reaction".

She said: "I'm not sure, having just heard this, whether a steel fence is really required. It may in fact just act as a magnet for protesters."

Tory Mid-Scotland & Fife MSP Brian Monteith said politicians should defer to police intelligence, but questioned why the �431m parliament building was not sufficiently secure already.

Individual liberties

He said: "I do rather wonder, after spending all the money on the Scottish Parliament, what we have in the way of a building which needs another fence to defend it.

"I do share a concern that the fence could itself act as a magnet for a parliament which will not be sitting when the G8 summit will be sitting."

The Liberal Democrat's Ross Finnie, a cabinet minister in the coalition Scottish Executive, said it was important to maintain security, but "the liberties of the individual and the right of peaceful protest is something we've got to get right".

We have looked at the possibility of some sort of security barrier around sites during the G8 Summit and the likelihood is that plan will go ahead Lothian and Borders Police spokeswoman

David Cairns, the Labour election candidate for Inverclyde, said he would not criticise the recommendations of the security forces and police.

He added: "The G8 has got an enormous agenda - it's talking about the future of Africa and global warming, two of the biggest issues facing our planet today.

"It's vitally important that people can turn up and protest peacefully, but if people are going to use this to forward their own kind of anarchist agenda, then clearly we've got to take every precaution against that."