The full extent of ministerial powers have been revealed by a committee of MPs.

Details of the sweeping but little understood powers of the Royal Prerogative were released on Monday by the Commons public administration committee.

As part of the agreement with the Queen, the government is allowed to make treaties, hire and fire ministers, control the supply of money, regulate the civil service, declare war and deploy armed forces.

The prerogative is an ancient right handed down from monarchs to ministers and the move to clarify its extent is part of a bid to increase transparency and accountability in government.

Currently there is not even an accepted definition of what the prerogative is.

It was also revealed that the committee is considering a law that would require parliament's permission before ministers and use prerogative powers.

The committee highlighted the fact that the vote over war in Iraq was granted as a favour by the prime minister and was not a constitutional demand.

Three facts were highlighted by the MPs as part of their initiative.

A power of mercy, which had been used to "save condemned men from the scaffold", is now used to correct errors in prison sentences.

New powers cannot be invented by ministers hoping to extend their influence on key issues.

And some ancient abilities remain available but have, fortunately, fallen out of use.

Under the Royal Prerogative, the government still has the power to "press men into the Navy" - or press ganging as it was originally known.

"The government is taking a valuable constitutional step away from the Middle Ages," said committee chairman Tony Wright.

"Ministers should be required to explain to parliament where their powers come from and how they intend to use them.

"The case of war powers is especially significant. Although the Commons had an opportunity to vote, there is no guarantee that this chance will be granted in the future."