Britain intercepted phone calls and monitored computers used by officials taking part in two high-level international finance meetings in London in 2009, a British newspaper said on Sunday.

The Guardian said some delegates from countries in the Group of 20 – which comprises top economies around the world – used internet cafes that had been set up by British intelligence agencies to read their e-mails.

The report was published hours before leaders of the G8 countries – all of which are in the G20 - started a two-day summit in Northern Ireland.

The Guardian said it had seen classified documents that detailed secret monitoring by British intelligence officials at a G20 leaders summit and a finance ministers’ meeting in 2009 and suggested it had been sanctioned at a senior level by the government of former Prime Minister Gordon Brown.

The aim of the monitoring appeared to have been to get an edge in the meetings and targets including South Africa and Turkey, the report said.

A spokesman for Britain’s foreign ministry declined to comment. The Labour party, which held power in 2009, was not immediately available for comment.