Former US president Barack Obama has penned his first article since leaving the Oval Office last Friday (20 January). The piece, published in a prestigious medical journal, takes aim at Republicans' health care plan, or lack thereof.

"Republicans' plan to repeal the [Affordable Care Act] with no plan to replace and improve it is so reckless," Obama wrote in the The New England Journal of Medicine on Thursday, 26 January.

"What the past eight years have taught us," Obama said, "is that health care reform requires an evidence-based, careful approach, driven by what is best for the American people."

Obama's article arrives a week after President Donald Trump signed an executive order designed to disrupt the implementation of the Affordable Care Act (ACA), popularly known as Obamacare. Trump signed the order in one of his first acts President on Inauguration Day, during the afternoon of 20 January.

Trump's order gives the states and others, including healthcare insurers and providers, the flexibility to circumvent the ACA and "waive, defer, grant exemptions from, or delay the implementation of any provision or requirement of the Act" that would put a financial burden on any state "or a cost, fee, tax, penalty, or regulatory burden on individuals", insurance and healthcare providers.

In an interview a week before his inauguration, Trump said he was nearing completion of a plan to provide healthcare "insurance for everybody" in the US. Trump did not reveal the specifics of his plan during the 15 January interview.

"It's very much formulated down to the final strokes. We haven't put it in quite yet but we're going to be doing it soon," Trump said. He added he is waiting for his Secretary of Health nominee Tom Price to be confirmed before moving ahead with an ACA replacement.

Before Trump said he would offer healthcare for all Americans, Republicans were poised to begin repealing ACA without anything to replace it on the second day of Congress, on 4 January. The move would have left millions of Americans without healthcare insurance.

"Rather than jeopardise financial security and access to care for tens of millions of Americans, policymakers should develop a plan to build on what works before they unravel what is in place," Obama wrote in the medical journal. "Persistent partisan resistance to the ACA has made small as well as significant improvements extremely difficult," he said.

Former president Barack Obama embraces a staff member before boarding Special Air Mission 28000, a Boeing 747 which serves as Air Force One, in Maryland 20 January 2017 Reuters/Brendan McDermid

On Monday (23 January), two Republican senators pushed forward their own plan to partially replace ACA, but also allow some states to keep the act if they find it's working for them.

"While the ACA provides very valuable assistance. The system created by the law is under significant financial stress," said Maine Republican Senator Susan Collins, citing an average increase in insurance premiums of 25% across the 50 US states. Collins and Louisiana Senator and physician Bill Cassidy are proposing The Patient Freedom Act as a replacement to the ACA.

Research by the fact-checking organisation found that the "25% increase" claim was no accurate, as more than 80% of people who face an increased cost of healthcare under the ACA are eligible for tax credits. The tax credits reduce the cost of insurance to pre-ACA levels, or below, but are income-dependant.

This bill would allow states to keep the ACA "if it's working for their residents", Collins said, noting that under Obama's health care plan insurance was extended to 14 million poor Americans.

Collins and Caddidy's bill would keep provisions of the ACA that allow young people to stay on their parent's health insurance policy and a rule that health insurers can't discriminate against people who have preexisting conditions. Several Republican Governors are already fighting to keep the ACA and met with members of the Senate last week.

"I am the first to say we can make improvements," Obama wrote. But he pointed out the success of his act in creating "better-quality and lower-cost care for tens of millions of seniors, individuals with disabilities, and low-income families covered by Medicare, Medicaid, and the Children's Health Insurance Program."

"This approach of 'repeal first and replace later' is, simply put, irresponsible," Obama said. "If a repeal with a delay is enacted, the health care system will be standing on the edge of a cliff."