Former US president Bill Clinton has hit out at Obamacare, calling the system "crazy" despite his wife's pledge to retain and improve the Affordable Care Act.

Clinton's comments came at a rally in Flint, Michigan on Monday (3 October) and were seized upon by the Trump campaign, which then claimed that Democrats were coming round to its belief that the healthcare system was failing.

"You've got this crazy system where all the sudden 25 million more people have healthcare and then the people are out there busting it, sometimes 60 hours a week, wind up with their premiums doubled and their coverage cut in half," Clinton said in comments carried by The Hill.

"It's the craziest thing in the world."

Hillary Clinton has repeatedly stated she is not prepared to get rid of Obamacare and is instead campaigning on the promise of maintaining and improving the system – something she has criticised her GOP rival for failing to embrace.

During her campaign to become the Democrat nominee, Clinton said there was no way she would allow Obamacare to be scrapped, stating at a Louisiana rally in September 2015, which was covered by CNN:

"All of the Republicans candidates for president are determined to get rid of the Affordable Care.

"I will tell you, I am not going to let them rip away the progress we made, I am not going to let them tear up that law, kick 16 million people off health coverage and force this country to start the health care debate all over again. Not on my watch."

And the Democrat nominee has underlined her commitment to the act, with her campaign page promising she will "Defend and expand the Affordable Care Act, which covers 20 million people".

It adds: "Hillary will stand up to Republican-led attacks on this landmark law—and build on its success to bring the promise of affordable health care to more people and make a "public option" possible. She will also support letting people over 55 years old buy into Medicare."

Bill Clinton's apparently contradictory statement to his wife's campaign pledge has been seized upon by the Trump campaign, which has long promised the GOP candidate would do away with Obamacare if he is elected.

"With premiums continuing to skyrocket, state insurance markets collapsing and businesses struggling to comply with its job-killing mandates, even Democrats like Bill Clinton are coming to realise just what bad public policy ObamaCare really is," Trump spokesman Jason Miller said in a statement to The Hill.

However, Bill Clinton's spokeswoman insisted that the ex-President supported the act but wanted to see improvements made.