Mr Blair will be a part-time adviser to JP Morgan, where he is expected to provide political and strategic advice and take part in some client events.

The former PM, who is currently serving as an unpaid international envoy in the Middle East, declined to say how much he would be earning. But the Financial Times newspaper quoted a New York recruitment consultant who said the job was likely to be worth more than £500,000 a year.

Mr Blair told the FT that he expected to agree to "a small handful" of similar appointments with other companies, adding: "I have always been interested in commerce and the impact of globalisation.

"Nowadays, the intersection between politics and the economy in different parts of the world, including the emerging markets, is very strong."

JP Morgan chief executive Jamie Dimon told the newspaper he had personally phoned Mr Blair.

"I went to visit him and we hit it off," he said.

Mr Dimon said Mr Blair would be "enormously valuable" to the company. "There are only a handful of people in the world who have the knowledge and relationships that he has."