At the White House Correspondents' Dinner a year ago, President Barack Obama teased Hillary Clinton over her six-figure speeches to Wall Street banks. "If this material goes well, I'll use it at Goldman Sachs next year," he said. "Earn me some serious Tubmans."

Less than 100 days after leaving office, Mr Obama has followed through: accepting a $400,000 speaking fee from Cantor Fitzgerald, the mid-sized investment bank.

On Tuesday a person familiar with the arrangement confirmed that Mr Obama had agreed to appear as the keynote speaker at Cantor's annual healthcare conference in September. The person declined to comment on what the former president might do with his fee, which is nearly twice the $225,000 price commanded by Mrs Clinton during three speeches to Goldman in 2013.

Mr Obama could not be reached for comment.

During his time in office the former president's relations with Wall Street often appeared strained — particularly in 2009, when he called bankers "fat cats" who kept drawing big bonuses while America went through a deep recession. Republican critics said that his landmark piece of rulemaking after the financial crisis, the Dodd-Frank Act of 2010, went much too far in its efforts to curb risk-taking at the biggest banks.

Since leaving the White House in January Mr Obama has kept a mostly low profile, resurfacing this week at the University of Chicago, at the future site of his presidential library.

Two months ago Penguin Random House agreed to pay more than $65m for the global rights to two books to be written separately by Mr Obama and his wife, Michelle. A blockbuster auction had already set a record for US presidential memoirs.

The speaking deal, which was first reported by Fox Business, is a coup for Cantor. The company has spent much of the past decade and a half trying to recover from the terrorist attacks in New York in September 2001, when it lost more than two-thirds of its staff.

Howard Lutnick, the bank's chairman and chief executive, backed Jeb Bush, the Republican candidate defeated by Donald Trump in last year's contest, according to campaignmoney.com. Another site, opensecrets.org, lists Mr Lutnick as a big fundraiser for John McCain, Mr Obama's Republican rival in the 2008 race for the White House.

Cantor launched its healthcare conference in New York two years ago, describing it as an opportunity to introduce investors to executives at dozens of the biggest healthcare companies.

Jonathan Westin, executive director of New York Communities for Change, a Brooklyn-based non-profit organisation, said he was dismayed to learn of Mr Obama "doing favours" for big banks.

"It feels like we're relying on the same tactics that got us in this mess in the first place — cosying up to Wall Street and alienating the entire Democratic base," he said.

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