Donald Trump has “never” taken the US presidency seriously and lacks the skills to grow into the job, his predecessor Barack Obama will say Wednesday at the Democratic convention.

“I did hope, for the sake of our country, that Donald Trump might show some interest in taking the job seriously…. But he never did,” the 44th president will say, according to excerpts of his speech released by convention organizers.

“He’s shown no interest in putting in the work, no interest in finding common ground,” Obama said in a series of deeply critical comments about the sitting president.

“Donald Trump hasn’t grown into the job because he can’t.”