In a review of the 55,000 federal oil and gas leases issued to energy companies by the Interior Department from 1987 to 1996, the General Accountability Office found that the vast majority expired without being drilled, and an even smaller amount actually produced oil and natural gas.

"We do not agree that Interior is pursuing expedited development of oil and gas leases," the report reads.

holding leases

Energy companies currently hold leases but are not producing on about 68 million acres (27.5 million hectares) of federal land - property that has the potential to double domestic oil production. About a third of the oil produced in the US in 2007 came from public lands.

The GAO found that current practices to expedite drilling, such as increasing the rent on federal lands not being drilled, did not do enough to spur production.

Only about 26 per cent of offshore leases and six per cent of federal leases on land issued from 1987 to 1996 had been drilled by 2007.

federal leases

The percentage that produced oil and gas was even smaller - 12 per cent offshore and five per cent on land.

The report recommends that the department consider measures used by states and private landowners to jump-start drilling, such as offering a lower royalty rate for faster production and shortening the term of the lease.

In a letter in response, Assistant Secretary Stephen Allred said that environmental reviews delay development on federal lands.

He also said that faster production in some areas could have "adverse consequences," but did not elaborate on what exactly he meant.

-AP