A UK Cabinet Office spokesperson told the BBC that, as a future heir to the throne, it was "appropriate that he (Duke of Cambridge) is regularly briefed on government business".
The revelation follows a Guardian report that his father, Prince Charles, receives such material routinely, along with UK monarch Queen Elizabeth II.
The second in line to the throne is sent confidential papers from the very top of government "occasionally" and "when relevant", according to a royal source.
Earlier this week, Republic received four chapters of the Cabinet Office's "precedent book" - released after a three- year freedom of information battle.
The book shows Prince Charles, the Queen, ministers and a handful of others get papers from cabinet and ministerial committees.
"There is no mention of this (Prince William's) access in the documents released this week. It appears to be a free for all. We support Labour's call for an inquiry, so we can know how much information is being handed to which royals," said Graham Smith, chief executive of Republic.
Labour MP Paul Flynn called for a parliamentary inquiry and said the access made Prince Charles the UK's "best- informed lobbyist".
