The Daily Telegraph reported Monday the heir to the throne has had 36 meetings with members of the Conservative-Liberal Democrat Cabinet since 2010. In the equivalent period in the last Labor government he met 23 times with Cabinet ministers.
The prince's office said the meetings are part of his job.
"Official meetings are important to the prince as heir to the throne and ministers from successive governments have found that he brings important insights," a spokesman said.
Graham Smith of Republic, a group that wants to abolish the monarchy, said the prince appears to be ignoring some of the biggest government departments, focusing on those dealing with his interests, which include the environment, architecture, healthcare and alternative medicine and country life.
"He has a more sympathetic ear among Conservative ministers than he did under Labor and he is exploiting that to full effect and ramping up his lobbying," Smith said.
Charles, who turns 65 in November, has occupied the position of heir to the throne longer than anyone else in British history. He has tried to use his position to boost causes he cares about while obeying the rule that the royal family must stay out of politics.