The entire future of Shell's drilling plans in the Arctic was put in doubt on Friday after two of Barack Obama's most trusted advisers called for a permanent halt to oil exploration.

In a piece for Bloomberg news, Carol Browner, who was Obama's climate adviser during his first two years in office, and John Podesta, who headed his 2009 transition team, said they now believed there was no safe way to drill for oil in the Arctic.

Their opinions come at a critical time for Shell, which has invested six years and nearly $5bn trying to gain access to the vast undersea reserves of oil and natural gas in the Arctic ocean.

The Obama administration this month launched a high-level review of Shell's plans for the Arctic, after a series of equipment failures and safety and environmental lapses.

The company is also struggling to repair or replace its Kulluk oil rig, which ran aground over the New Year, in order to return to the Arctic when the drilling season re-opens in July.

Now two of Obama's advisers are suggesting Shell and other companies should not be operating in the Arctic at all.

"Developers and Barack Obama's administration assured us these operations would be safe, thanks to strict oversight and new technology. Now it seems that optimism was misplaced," Browner and Podesta write in a piece for Bloomberg View.

"Following a series of mishaps and errors, as well as overwhelming weather conditions, it has become clear that there is no safe and responsible way to drill for oil and gas in the Arctic ocean."

Both writers are associated with the Center for American Progress, which operates as an incubator of liberal ideas and has been almost uniformly supportive of Obama's policies.

Campaign groups saw the shift from Podesta and Browner as a sign that Obama, too, could be open to reversing his initial decision to open up the Arctic to offshore drilling.

"The messengers are what make this particular op-ed important," said Michael LeVine, senior counsel for Oceana.

There was no immediate response from Shell.

But, as Browner and Podesta point out, there has been growing doubt about the entire idea of drilling for oil in the Arctic – from scientists, banks and insurers, and even rival oil companies, such as Total.

Those doubts escalated throughout Shell's first season in the Arctic, which brought a series of near-disasters, including the grounding of its Kulluk rig on New Year's Eve.

Last week, the departing interior secretary, Ken Salazar, admitted he had never "felt comfortable" with Shell's preparations for drilling in the harsh environment of the Arctic.

"It may be that Shell isn't even ready to move forward with drilling in 2013," Salazar said.

Browner and Podesta went one further on Friday, arguing: "The Obama administration shouldn't issue any new permits to Shell this year and should suspend all action on other companies' applications to drill in this remote and unpredictable region."

The two concluded: "It has become clear that the best Shell's money can buy just isn't good enough."