Prince Charles, the Duke of Cornwall, is at the centre of a political row after it was revealed that members of his staff had "secretly" worked in Westminster.
The heir to the throne's staff were reported to have under taken placements at departments linked to his key interests of rural affairs and the environment.
However ministers were said to be unaware of the placements and questioned whether the Duke was overstepping the mark.
He also called for clarity over what the Royal staff did and whether they exerted any influence on policy.
One reportedly claimed it was "undemocratic" and said: "There are questions that need to be answered about who agreed it.
"It raises questions about whether Prince Charles is exceeding his position as constitutional monarch in waiting."
Accord to the Sunday Times, three of the Prince's staff had been sent to work in Whitehall, with the secondments being arranged on an 'ad hoc' basis.
One of the Prince's employees was seconded to a policy team at Defra, the environment and rural affairs ministry, for 14 months while another spent two years at the Cabinet Office.
A Clarence House spokesman said the placements were simply about career development.
"All three secondments were suggested on the basis of professional development and the paperwork was arranged by the relevant HR departments."
He refused to confirm their identities, the position they held and who authorised the placement. The reports emerged during a month when the role of the heir to the throne – and his motives – has rarely been out of the spotlight.
Last week, MPs said they would investigate Prince Charles's controversial veto over government legislation that affects Duchy of Cornwall interests.
It had emerged ministers have been forced to seek permission from the heir to the throne to pass at least a dozen government bills.
The royal veto, which critics say influences ministers if not used, will be examined by the House of Commons political and constitutional reform committee next month. The same week it was disclosed that Prince Charles had held 36 meetings with ministers since the Government took power.