Former President Barack Obama has cautioned young Democrat activists against using snappy slogans such as "defund the police" if they want to bring about genuine reforms in the US.

Defund the Police became a widely-used phrase after the killing of George Floyd by Minneapolis police in May.

Mr Obama said "you lost a big audience the minute you say it", making it "a lot less likely" to effect change.

His comments received a backlash from some key black progressive Democrats.

Minnesota congresswoman Ilhan Omar tweeted "it's not a slogan but a policy demand... for equitable investments and budgets for communities across the country".

Cori Bush, a newly-elected congresswoman in Missouri, tweeted that the slogan was a "mandate for keeping our people alive", while Charles Booker, Kentucky's youngest black state lawmaker, tweeted: "Instead of conceding this narrative, let's shape out own".

Mr Obama made his comments while speaking to the Snapchat political show Good Luck America about the importance of word choice in marketing ideas.

"If you believe, as I do, that we should be able to reform the criminal justice system so that it's not biased and treats everybody fairly, I guess you can use a snappy slogan, like Defund the Police, but, you know, you lost a big audience the minute you say it," he said.

"If you instead say, 'Hey, you know what Let's reform the police department so that everybody's being treated fairly,' suddenly a whole bunch of folks who might not otherwise listen to you are listening to you."

Defund the Police became part of the call for change during mass Black Lives Matter protests following the killing of Mr Floyd, and Breonna Taylor in Kentucky in March, at the hands of the police.

"Defunding" advocates want to see police departments' budgets slashed and funds diverted to social programmes to avoid unnecessary confrontation and heal the racial divide.

President-elect Joe Biden has previously said he does not support defunding the police, but wants to invest in community projects and social programmes to lessen the burden on the police.

In the same interview, Mr Obama said it was important to ensure that progressive members of the Democratic party have their voices heard, saying "new blood is always good".

With reference to New York congresswoman Alexandria Ocasio-Cortez, he said: "She speaks to a broad section of young people who are interested in what she has to say, even if they don't agree with everything she says. You give her a platform."