Mr Walker’s views carry weight because he is a non-partisan figure in charge of the Government Accountability Office, often described as the investigative arm of the US Congress.
While most of its studies are commissioned by legislators, about 10 per cent – such as the one containing his latest warnings – are initiated by the comptroller general himself.
In an interview with the Financial Times, Mr Walker said he had mentioned some of the issues before but now wanted to “turn up the volume”. Some of them were too sensitive for others in government to “have their name associated with”.
“I’m trying to sound an alarm and issue a wake-up call,” he said. “As comptroller general I’ve got an ability to look longer-range and take on issues that others may be hesitant, and in many cases may not be in a position, to take on.
“One of the concerns is obviously we are a great country but we face major sustainability challenges that we are not taking seriously enough,” said Mr Walker, who was appointed during the Clinton administration to the post, which carries a 15-year term.
The fiscal imbalance meant the US was “on a path toward an explosion of debt”.
“With the looming retirement of baby boomers, spiralling healthcare costs, plummeting savings rates and increasing reliance on foreign lenders, we face unprecedented fiscal risks,” said Mr Walker, a former senior executive at PwC auditing firm.
Current US policy on education, energy, the environment, immigration and Iraq also was on an “unsustainable path”.
“Our very prosperity is placing greater demands on our physical infrastructure. Billions of dollars will be needed to modernise everything from highways and airports to water and sewage systems. The recent bridge collapse in Minneapolis was a sobering wake-up call.”
Mr Walker said he would offer to brief the would-be presidential candidates next spring.
“They need to make fiscal responsibility and inter-generational equity one of their top priorities. If they do, I think we have a chance to turn this around but if they don’t, I think the risk of a serious crisis rises considerably”.