Six further control orders served

Control orders were introduced under 2005 anti-terrorism legislation

Police have served six new control orders on terrorism suspects in the past quarter, according to the latest Home office figures.

In a Parliamentary statement, ministers said that as of 10 June there were 15 orders in place.

More than 30 people have been subjected to the orders since they were first introduced - seven of whom absconded.

The orders are designed to restrict the activities of suspects who officials fear pose a threat if left unmonitored.

British citizens

In the latest statement, Security Minister Tony McNulty said that between 11 March and 10 June 2008 six control orders had been made and served on individuals, one order had renewed and two revoked.

Mr McNulty said one further order had been made but not yet served.

Under the rules, the home secretary approves an order on the advice of the security services. The papers are then served in person by a police officer, who tells the suspect what it means.

"In total, 15 control orders are currently in force, three of which are in respect of British citizens," said Mr McNulty.

"Two individuals subject to a control order live in the Metropolitan Police Service area; the remaining individuals live in other police force areas."

He added that all the control orders were "non-derogating", meaning they complied with the government's obligations to observe human rights.

Secret evidence

Critics of control orders say they are impossible to effectively challenge because they rely on secret evidence. In each case there are open and closed hearings.

The closed hearings involve lawyers called special advocates, who argue against the intelligence assessments used to make the case for an order - but the suspect cannot help the advocate build the case because he has not seen the secret material.

Only one suspect subject to a control order has so far won at all stages and walked out of court a free man.

However, the government's terrorism laws watchdog has backed the system, saying there are cases where the special advocates have effectively challenged secret material on their client's behalf.

The statement revealed there are currently 11 outstanding appeals against control orders pending at the High Court.

During the same three months, a judge in another challenge agreed the Home Office should increase one suspect's curfew - but banned officials from new restrictions on whom he could meet in his home.

Another potentially important ruling came on 9 April when the High Court ruled that the home secretary had not provided enough details of the secret evidence for the order to be compatible with human rights obligations. Ministers are appealing against that decision.

"Control orders continue to be an essential tool to protect the public from terrorism, particularly where it is not possible to prosecute individuals for terrorism-related activity and, in the case of foreign nationals, where they cannot be removed from the UK," said Mr McNulty.