The specialist underwear is part of a complete flame-retardant kit in case of petrol-bomb or incendiary attacks by protesters or terrorists.

After violent disturbances at previous G8 meetings, Scots police chiefs are taking no chances with the event at Gleneagles from June 6.-8.

A police source said yesterday: "Supposedly the underpants are designed not to melt if we are hit by a petrol bomb. It probably won't be the most comfortable summer clothing, but we'll need it."

Security at the Perthshire summit - where Tony Blair will host US president George W. Bush and other VIPs - will be the tightest ever seen in Scotland.

Officers from every police force in the country will be drafted in.

Anarchists, anti-globalisation yobs and even al-Qaeda fanatics are seen as potential threats. Last week it was claimed up to 200 000 demonstrators could descend on Edinburgh before the event.

Tayside Chief Supt Brian Powrie, in charge of G8 planning, said: "Officers will get appropriate equipment for any situations they may face."