The island state would need as much as $21bn in aid over the next two years to keep the government operating and cover the salaries of state employees, such as police and teachers, according to Natalie Jaresko, executive director of the federal control board responsible for overseeing the country’s finances.

In a testimony prepared for the House Natural Resources committee on Tuesday, Jaresko said: “The hard truth is that the island now needs help – emergency and restoration funds and assistance on an unprecedented scale.”

The devastation caused by the hurricanes has deepened the financial crisis the island was already facing. It has $74bn of debt and was at the centre of US’s biggest public bankruptcy process. 

“Before the hurricanes, the board was determined that Puerto Rico and its instrumentalities could achieve balanced budgets, work its way through its debt problems, and develop a sustainable economy without federal aid,” Jaresko said.

“This is simply no longer possible.”

Local authorities estimate that between $45bn and $95bn of damage has been caused by the storms. The country is currently revising its fiscal plans to account for the hurricane.

The US Congress has so far approved $4.9bn in low-interest loans for the island and the US Virgin Islands as part of a $36.5bn aid package.

The board has also estimated that the country’s population could drop by 5% before the end of the year.

Jaresko said: “We know that Puerto Rico is experiencing a massive population exodus, but the exact amount of that exodus is unknowable.”

The OECD’s Development Assistance Committee changed its aid rules last week, extending eligibility to countries hitherto deemed to wealthy to receive aid in the event of a humanitarian crisis.