Republic campaigns for the to Queen be replaced with an elected, democratic head of state and the monarchy to be abolished. The organisation's CEO Graham Smith criticised the Prince of Wales' excessive spending on travelling around the world in luxury during an interview with Express.co.uk.
Mr Smith said: "It is a competition between the royals on who can spend the most.
"Obviously the Queen spends an awful lot because she is the head of state and the head of the firm so she is responsible for most of that £345 million a year.
"Prince Charles and his brother Andrew are particularly ostentatious in their spending.
"They travel all around the world in considerable luxury.
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Prince Charles and Prince Andrew's spending was criticised
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"It is a tough competition, they are all as bad as each other."
During the same interview, Mr Smith branded the Royal Family for as unaccountable and secretive in a scathing attack on the institution.
Republic's CEO told Express.co.uk that the cost is just one symptom of why the UK should get rid of the monarchy.
Mr Smith said: "The cost is one symptom of why the monarchy should be abolished.
"They get away with it because it is unaccountable.
"No one can get rid of them as individuals, they have to get rid of the whole institution.
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Republic campaigns for the Queen to be replaced with an elected head of state
"They get away with it because they are secretive and do not reveal the information about money being spent and what they are getting up to behind closed doors.
"We are supposed to be a democracy, we have argued about democracy and the will of the people for the last four years.
"We then don’t turn that same logic to the monarchy.
"So, it does not live up to the standards that we should expect of an institution in this country in this day and age."