Former United States President Barack Obama has accused Donald Trump of treating the US presidency like “one more reality show”, in a withering speech to the Democratic convention.

Obama said his Republican successor “hasn’t grown into the job because he can’t”.

On Wednesday night, Obama unleashed possibly his most scathing attack yet about Mr Trump, speaking live from the Museum of the American Revolution in Philadelphia.

He said: “Trump has shown no interest in putting in the work. No interest in finding common ground.

“No interest in using the awesome power of his office to help anyone but himself and his friends.

“No interest in treating the presidency as anything but one more reality show that he can use to get the attention he craves.”

He said the consequences of the Trump presidency have been “our worst impulses unleashed, our proud reputation around the world badly diminished, and our democratic institutions threatened like never before”.

The former president lamented “the circus of it all, the meanness and the lies and the conspiracy theories”.

“Do not let them take away your power,” he implored American voters. “Do not let them take away your democracy.”

Mr Obama encouraged voters to elect his former vice-president, Mr Biden, in 76 days’ time – praising him as “my friend” and “a brother”.