<P> The concept of a veto body originated with the Roman consuls and tribunes . Either of the two consuls holding office in a given year could block a military or civil decision by the other; any tribune had the power to unilaterally block legislation passed by the Roman Senate . </P> <P> The institution of the veto, known to the Romans as the intercessio, was adopted by the Roman Republic in the 6th century BC to enable the tribunes to protect the interests of the plebs (common citizenry) from the encroachments of the patricians, who dominated the Senate . A tribune's veto did not prevent the senate from passing a bill, but meant that it was denied the force of law . The tribunes could also use the veto to prevent a bill from being brought before the plebeian assembly . The consuls also had the power of veto, as decision - making generally required the assent of both consuls . If one disagreed, either could invoke the intercessio to block the action of the other . The veto was an essential component of the Roman conception of power being wielded not only to manage state affairs but to moderate and restrict the power of the state's high officials and institutions . </P> <P> In Westminster systems and most constitutional monarchies, the power to veto legislation by withholding the Royal Assent is a rarely used reserve power of the monarch . In practice, the Crown follows the convention of exercising its prerogative on the advice of its chief advisor, the prime minister . </P> <P> Since the Statute of Westminster (1931), the United Kingdom Parliament may not repeal any Act of the Parliament of the Commonwealth of Australia on the grounds that is repugnant to the laws and interests of the United Kingdom . Other countries in the Commonwealth of Nations (not to be confused with the Commonwealth of Australia), such as Canada and New Zealand, are likewise affected . However, according to the Australian Constitution (sec. 59), the Queen may veto a bill that has been given royal assent by the Governor - General within one year of the legislation being assented to . This power has never been used . The Australian Governor - General himself or herself has, in theory, power to veto, or more technically, withhold assent to, a bill passed by both houses of the Australian Parliament, and contrary to the advice of the prime minister . This may be done without consulting the sovereign as per Section 58 of the constitution: </P>

The house and senate can override a governors veto with a vote