Former US vice president Joe Biden has said that he regrets supporting the "tough-on-crime" drug legislation of the 1990s.

Mr Biden, who was first elected to public office the year after Martin Luther King’s assassination, made the comments at an event to commemorate the birthday of the civil rights leader.

Speaking at the event at the Mayflower Hotel in Washington, Mr Biden spoke about his remorse over a bill that created different legal standards for powdered cocaine and street crack cocaine.

“It was a big mistake that was made,” Mr Biden said of the measure, which has been criticised as disproportionately affecting black Americans. We were told by the experts that ‘crack, you never go back’, that the two were somehow fundamentally different. It’s not. But it’s trapped an entire generation.”

The former senator, who helped write the 1994 crime bill now cited as having led to an era of mass incarceration, said that he “may not have always gotten things right” in regards to criminal justice.

Mr Biden’s remarks served as a pre-emptory move to head off criticism of his past policy decisions and made clear that he is both seriously considering a presidential bid and recognises the hurdles he would face from his increasingly progressive party.

But he was not the only potential White House contender in attendance at Washington’s Mayflower Hotel with a record on criminal justice issues that leaves some African-Americans uneasy.

Former New York Mayor Michael Bloomberg also spoke. But he avoided any mention of the controversial policing tactic he supported in New York called “stop-and-frisk,” which gave police officers sweeping powers to detain – and sometimes harass – those suspected of committing crimes, particularly in neighbourhoods with predominantly non-white residents.

Mr Bloomberg did discuss a series of events that had shaped his recent thinking about race. In one example, he said he had recently learned about the deadly race riots in which white residents destroyed the Greenwood district of Tulsa, Oklahoma, in 1921 and murdered several dozen black residents.

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“It’s up to us to bring these stories out of the shadows so that they never happen again,” Mr Bloomberg said. “We don’t need to erase history, we need to face up to history.”

Several audience members said they appreciated how Mr Bloomberg and Mr Biden spoke to Martin Luther King’s legacy and the issues of civil rights.

But it was not difficult to find scepticism in the audience about whether they will be able to reckon with their past policies.

“It all just sounds like 2020 is getting closer,” said Christian Taylor, a 29-year-old consultant who attended the breakfast.