The former Labour prime minister believes now is the time to speak up and will appear on a joint platform with Labour leader Ed Miliband in July at an event celebrating the Olympics.

Blair’s wife, Cherie, will also attend, making it a rare appearance for the two of them in public.

A source close to Blair said: “He wants to re-engage in the UK. He has things to say and he thinks it’s the right time. The question is how he re-enters the UK scene without re-entering domestic politics and interfering with the Labour Party.”

The former PM has hired Rachel Grant, an ex-Downing Street and Whitehall press officer, now communications director at the National Endowment for Science, Technology and the Arts (Nesta) charity.

This week marks 15 years since Blair first entered Downing Street, after he won a landslide victory over John Major’s Conservatives.

Blair has built a £20 million fortune since he left office five years ago, working in foreign affairs and business interests.

A spokesman for Miliband said: “Tony Blair is a very big, successful Labour figure who won three general elections. He talks to Ed regularly and we would be delighted to see him re-engaging in British politics.”