US President-elect Joe Biden has condemned Donald Trump’s refusal to accept defeat in the presidential election, saying it sent “a horrible message about who we are as a country”.

Biden said he was confident Trump knew he was not going to win and had shown “incredible irresponsibility”.

Trump has launched lawsuits alleging unsubstantiated election fraud.

He has now also invited state lawmakers to the White House, hinting at a possible change in tactics.

Michigan’s Republican lawmakers have been asked to meet him there on Friday.

All but one of Trump’s challenges has failed to make any real headway.