The activists made the allegations in a news conference outside Edinburgh Sheriff Court. Some of their complaints concerned practices that are standard in Scotland. Three of them were arrested in Glasgow on Friday and held in custody until Monday. Right or wrong, there is nothing unusual in that. But they also alleged they suffered psychological torture inside a Glasgow police station.

Dr Martin Kraemer, a protester arrested in Glasgow, said: "I got woken up 73 times in these 4 days. Every night we had a wake-up at 2 o'clock, at 3 o'clock at 4 o'clock in the morning and these wake-ups would get more and more violent."

Zahra Quadir, another protester arrested in Glasgow, said: "The way they treated us, in solitary confinement, three nights, four days with no communication with anyone. The food and the water they gave us made us sick. I was very disappointed by the Scottish system."

In response to the allegations the Association of Chief Police Officers issued a statement. It said that all of the officers involved in the G8 summit demonstrated a thoroughly professional and efficient service at all times. That includes the care in custody of those who were arrested throughout the week.

But disquiet over what happened last week is not confined to the protesters themselves. The Scottish Human rights centre is compiling a dossier on the police operation. John Scott from the Scottish Human Rights Centre said: "Some people who want to complain about the police will not go to the police, and in Scotland as we don't have an independent police authority, that's the only choice they've got. So they may well come to us."

Just 20 formal complaints have made against the police so far - most of them concern events in the capital last Monday.