Last updated at 15:38 26 October 2007

The Pentagon was reeling last night from the American military's second major nuclear weapons blunder in a month.

Congress is demanding a full scale investigation and serious questions are being asked about the competence of the officers in charge of the world's mightiest arsenal.

The latest outrage came as Commander Michael Portland, the officer in charge of the USS Hampton, the most advanced nuclear attack submarine in the world, was fired after it was discovered that he had neglected to make basic daily safety

checks.

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Last month 70 US airmen were demoted after they lost track of six nuclear-armed cruise missiles and allowed them to be flown halfway across America by a bomber crew that didn't even know they were there.

The Pentagon said that it had lost confidence in Commander Portland's leadership after checks showed that he had failed to analyse the chemical and radiological properties of the submarine's nuclear reactor for a month.

It is considered vital that the reactor's condition be fully examined every day so that any malfunction can be caught early.

If something went wrong with the reactor it could lead to a devastating nuclear accident.

The USS Hampton, currently docked in San Diego, is armed with nuclear torpedoes, nuclear cruise missiles and a massive mine-laying arsenal.

US Navy officials said that it had also been discovered that logs on the USS Hampton had been filled out to make it appear the daily checks of the reactor water had actually been done.

Members of Congress are furious about the latest scandal especially as it follows so closely after the nuclear missile debacle.

In that incident a large US Air Force team failed to remove the nuclear warheads from six cruise missiles being flown by a B-52 bomber from North Dakota to Louisiana.

It was described as one of the worst known breaches of nuclear weapons procedures ever.

The incident sparked a so-called "Bent Spear" nuclear alert, one step down in military terms from a "Broken Arrow".

A "Broken Arrow" is triggered if a nuclear missile has been lost or detonated in a way that does not create the risk of nuclear war.

If the B-52 had crashed there would not have been a nuclear explosion but there could have been major plutonium leakage causing thousands of deaths.

Independent inquires are being launched into both the nuclear missile and the nuclear submarine incidents and Congress is planning hearings into the Pentagon's nuclear safety procedures.

An investigation is also underway into how the US Army came to accidentally fire a ground to air Patriot missile from a base in the Gulf Arab state of Qatar earlier this month.

The missile landed harmlessly in the desert but it could have brought down any aircraft in the vicinity and it has renewed charges in the Middle East that American soldiers can be trigger-happy and careless.