George Osborne made more than £300,000 in a month from speeches

George Osborne, the former chancellor, made more than £320,400 in a month from giving speeches to US banks, financial organisations and a university, his register of interests shows.

The senior Conservative, who is still an MP, appears to be a popular choice with American financiers, after he signed up to the Washington Speakers’ Bureau on leaving government.

Between 27 September and 27 October, he gave five speeches earning him between £28,000 and £81,000 each.

The most lucrative were two events for JP Morgan, the investment bank, at £81,174 and £60,578 each, one for Palmex Derivatives at £80,240, and another for the Securities Industry and Financial Markets Association for £69,992.

The cheapest was a one-hour address to the Hoover Institution at Stanford University, earning him £28,454.

The total he is expecting to receive for freelancing in just one month is almost four times his annual salary as a backbencher, which is £74,000.

The latest MPs’ register of interests also shows Michael Bloomberg, the former mayor of New York, paid more than £4,000 to allow Osborne and his wife, Frances, to attend a dinner in Paris.

The former chancellor is following in the footsteps of Tony Blair and Gordon Brown who also signed up to the agency. He is not earning anywhere near as much as the £200,000 a time that Blair was thought to command, but around the same as Brown, who donated fees of about £70,000 to his charitable foundation.

David Cameron does not have to declare his earnings after holding office because he stepped down as an MP in September.

He has given little indication of his plans for life after Downing Street other than chairing a panel of patrons on the expanded National Citizen Service, a summer camp he set up that is designed to instil social responsibility in young people as part of his “big society”.

However, it emerged earlier this month that Cameron would give a speech for the private equity firm Bain Capital in one of his first public engagements since his departure from No 10.

The former prime minister has signed a deal to write his autobiography, saying he will give a frank account of his time in Downing Street.