Barack Obama went on the offensive over his ailing healthcare reforms on Wednesday, challenging Republicans to suggest alternatives and insisting there was no going back to the previous system that left 43 million Americans uninsured.

As the White House sought to use recent improvements to its broken website to turn the public debate around, Obama spoke in front of a group of patients who had already benefited from other reforms under the Affordable Care Act.

"My main message today is: we're not going back," said the president. "That seems to be the only alternative that Obamacare's opponents have."

“If you don't like the law, then you have got to tell us specifically what you would do differently. You can't just say the system was working when 43 million went without health insurance.”

Earlier, House speaker John Boehner appeared flustered at a press conference on Capitol Hill when pressed by reporters about whether Republicans would propose their own reform legislation instead of merely calling for the repeal of Obamacare.

Ignoring a question from NBC News about what his favoured “patient-centric” approach would look like, Boehner turned to Fox News for a change of subject, only to be asked again whether there would be a bill. “We'll see,” he replied.

But Obama appeared to acknowledge at his own press event that the problems with the healthcare.gov website had caused enormous damage to the cause of health reform and distracted attention from the underlying benefits of his legislation.

“No one should have to worry about going broke just because someone in their family gets sick; we thought we were better than that,” he said. “That's what's gotten lost over the last couple of months as we focused, rightly, on fixing the website.”

Even with improvements to the consumer-facing front end of the website, the White House is far from out of the woods – hinting on Monday at a massive clean-up operation to make sure people who thought they had signed up are actually referred to insurers.

The Washington Post estimates as many as a one third of those who signed up since October 1 have been hit by these back end problems.

The White House insists it has now fixed the problems with so-called 834 forms, which are meant to provide financial details to insurers so they can complete the policy transaction.

But for the first two months of the website's existence, these payment processing glitches received lower priority from technicians who were focused on fixing the publicly visible parts of the website instead.

As a result, many of those who managed to enrol previously are now being contacted by officials and asked to check directly with insurers to make sure they have the cover they hoped for.

Insurers have also complained about the quality of information they receive about new customers signing up through healthcare.gov, although it is not clear if these complaints predate the 834 software upgrades that the White House insists were introduced at the weekend to address the problem.

Nevertheless, the White House appears confident enough now in the performance of the online insurance exchanges to redouble its political support for the programme in the days leading up to a December 23rd deadline for those seeking cover in 2014.

“We are not repealing it as long as I am president,” said Obama to loud applause from the young insurance recipients gathered around him in the White House executive office building.