Mr Biden attacked the outgoing president as Mr Trump continued to refuse to concede his defeat and actively hampered the transition.
The Democrat said the move was “outrageous” and that “there’s questions whether it’s even legal.”
“It’s hard to fathom how this man thinks. It’s hard to fathom,” said Mr Biden.
“It’s just outrageous what he’s doing.”
The lame duck president has lost a string of court cases in battleground states to unsuccessfully try and reverse his election losses.
A federal judge in Georgia threw out Mr Trump’s efforts to block the certification of results in that state, which will now be done on Friday. A hand recount in the Peach State confirmed Mr Biden’s victory there.
Mr Trump now has just one win and 32 losses in post-election litigation, according to reports.
The president-elect also warned that the country was “witnessing incredible irresponsibility” from Mr Trump and his Republican enablers.
And he warned that their actions were sending “incredibly damaging messages to the rest of the world about how democracy functions.”