The Government's spying services employ 6,000 people at GCHQ alone. MI5 headquarters, on Millbank in London, and MI6 headquarters, across the river in Vauxhall, employ about 2,000 each. According to MI5's own website, the spying agencies' budget is £1 billion a year. It is a big operation.

What do they do?

• In the mid 1970s the head of MI5, Michael Hanley, kept a file on the then Labour prime minister, Harold Wilson. MI5 also investigated other Labour government ministers. Some MI5 agents were involved in plots to discredit and oust Wilson.

• In the same period an MI5 operation in Northern Ireland distributed fake leaflets and pamphlets trying to discredit Labour Party leaders, even right-wing ones, as linked to the IRA.
• For decades MI5 vetted all important applications for jobs at the BBC, without telling the BBC's Chairman that they were doing it. This was revealed by the Observer in August 1985. MI5 had a list of one million people whom they damned as "subversives".

Until 1989 the spying services operated in legal darkness, where their budget was secret and the Government did not even notionally have the right to full reports on what they were doing.

After revelations in 1987 about the plotting against Wilson, the Thatcher government cleaned up the act a bit. The spying services now have a publicly-declared budget, and even their own website.

But, as we see from the latest revelations about the UN secretary general being bugged, no-one knows what they do behind the scenes.

The spying services' work against the left, or those whom their right-wing paranoia makes them see as "left", has been done none too competently. Harold Wilson did after all become prime minister, and resign when he wanted to resign for his own reasons.

Anything the spying services do against al-Qaida or other ultra-right terrorist groups is probably done no more competently. A democratic and open system of monitoring and checking on threats would do anything positive that MI5 can do better, and without the systematic threat to civil liberties and democracy that this large army of spies represents.

Scrap MI5!