Ministers have asked for the Prince of Wales's consent on 12 draft bills ranging from gambling to road safety over the last six years.
The Guardian newspaper reported, following a freedom of information request to the House of Commons, that Charles was consulted on legislation concerning the London Olympics, coroners, economic development and construction and housing and regeneration.
The Prince's consent is required if the bill affects the interests of the Duchy of Cornwall - the multi-million pound estate which provides the heir to the throne with his £18 million a year private income.
Republic, which campaigns for an elected head of state, called on Clarence House and the Government to publish details of all legislation altered as a result of what it branded a "constitutional loophole allowing (Charles) to veto Government bills".
Graham Smith, spokesman for Republic, added: "That such a loophole exists shows our constitution is fundamentally anti-democratic."
The Prince's spokesman said: "Parliamentary procedure determines that the Prince of Wales in his capacity as the Duke of Cornwall may be required to give his consent to Bills directly affecting the interests of the Duchy."
The Queen's Consent is also required if a bill affects the prerogative of the Crown or the interests of the Crown, the Duchy of Lancaster or the Duchy of Cornwall. Charles has frequently faced criticism over his contact with the Government and faced accusations of meddling.
Downing Street said the Prime Minister has no plans to change the laws and declined to confirm whether any planned legislation had been blocked or amended as a result of objections from the Prince.
A spokeswoman for Number 10 said that it was established protocol, as set out in the parliamentary bible Erskine May, that "the Prince's consent is required for a bill which affects the rights of the principality of Wales, the earldom of Chester or which makes specific reference to or makes special provision for the Duchy of Cornwall".
The latest edition of Erskine May adds: "The Prince's consent may, depending on circumstances, be required for a bill which amends an act which does any of these things. The need for consent arises from the sovereign's reversionary interest in the Duchy of Cornwall."