Spying is said to be the world's second oldest profession. Covert by definition, it is used against friends and allies, as well as enemies. However, Monday’s startling leaks published by the Guardian show, more than ever, how technology has hugely extended the scope of spying in a way that has unprecedented implications for personal privacy, corporate wealth, and the conduct of international relations.

The NSA and its close British partner, GCHQ, defend their activities on the grounds they are fighting terrorism and serious crime.Top-secret documents now reveal that they are also spying on Russia, Turkey, South Africa and other nations in operations that have nothing to do with terrorism or crime. The purpose is to give the UK a competitive and negotiating advantage. It is justified on legal grounds because the 1994 Intelligence Services Act says GCHQ can gather information “in the interests of the economic wellbeing of the United Kingdom”.Three years earlier, the Guardian revealed how GCHQ bugged a wide range of targets which on the face of it had nothing to do with the nation's security. The results included intelligence that would benefit British companies including the oil giants and banks. GCHQ even bugged the pope.

Leaks to the Guardian have revealed the huge capacity of NSA and GCHQ computers. The law cannot keep up with developments in technology, as intelligence officers admit. How the data is used - against terror suspects, but not innocent individuals - is, they admit, a matter of trust, not the law.

Leaks of the documents suggest it is impossible to quench the appetite of the intelligence agencies and their clients, notably the ministers to whom they are responsible. Britain's spies say they are ultimately accountable to ministers, the people who are urging the spies on.

One unanswered question is how bugging delegates to international conferences hosted by Britain can be justified when the security and intelligence agencies insist they need more resources to counter real threats. That question will become even more important as the capabilities of computers increase beyond the reach demonstrated by the latest leaks.

By arrangement with the Guardian