Members of Prince Charles' staff are working for the government, it has been revealed.
Three of the Prince's 'moles' have been seconded to Whitehall in the past five years, Clarence House said.
Suspicions that they had been posted in order to influence government policy were strongly denied, but an MP raised concerns and pledged to raise the matter in the House of Commons.
All three were said to be junior staffers who had been given the placements - which ranged from six weeks to two years - in order to develop their careers.
But some MPs have raised concerns about the placements, saying they will raise the issue in the Commons when Parliament returns next month.
Two of the staff concerned were seconded to the Cabinet Office while the third went to the Department for the Environment, Food and Rural Affairs. One has now left the Prince's employment.
A Clarence House spokesperson said: "We have had two secondments to government departments in the past two years. The secondments were suggested on the basis of professional development and the paperwork was arranged by the relevant HR departments.
"One secondment was one year and the other was for two years. Both have come to a natural conclusion. There was no official feedback mechanism and no regular meetings were attended with the Prince of Wales's Household.
"The secondments were on a like for like basis. One secondee has now left Clarence House and the other is due to return shortly after a sabbatical.
"Over the past five years, in addition to the two secondments already discussed, there has been one other secondment, for six weeks to the Cabinet Office. We have no new secondments planned at present."
The disclosure comes after it emerged last week that the Prince had had 36 private meetings with Cabinet ministers since the general election in 2010.
One unnamed minister told The Sunday Times that it raised questions as to whether the Prince was exceeding his position as a constitutional monarch in waiting.
"I think it's undemocratic," the minister was quoted as saying. "There is a question about what they are doing and whether they are influencing policy."
Labour MP Paul Farrelly said he would be raising the matter with ministers when the Commons returns following the summer recess.
"It raises constitutional questions about the influence the monarch in waiting has over policy and there will be questions in the House when it returns," he told The Sunday Times.