London: Members of Prince Charles’s staff have been secretly working full-time in key Whitehall departments linked to his interests.

One employee spent two years at the Cabinet Office while another was seconded to a rural policy team at Defra, the environment and food ministry, for 14 months.

Several current and former ministers said they had not been informed of the placements and expressed surprise and irritation at not being told.

One minister said: “There are questions that need to be answered about who agreed it. I think it’s undemocratic.

“It raises questions about whether Prince Charles is exceeding his position as a constitutional monarch in waiting. There is a question about what they are doing and whether they are influencing policy.”

Ministers said they were planning to raise the issue within government.

Secondments between government departments, businesses and charities are common, but they are usually transparent. By contrast, both the government and the prince’s office were reluctant to disclose details.

While confirming that three of the prince’s employees had been sent to work in Whitehall, his office refused to provide their identities or say what tasks they had undertaken. It also declined to reveal who had authorised the placements.

A spokesman for Clarence House said the secondments were arranged on an “ad hoc” basis. He added: “All three secondments were suggested on the basis of professional development and the paperwork was arranged by the relevant HR departments.”

Sources close to the prince said his staff and the government were “in constant contact to keep him up to speed on issues and current affairs”.

Foreign and Commonwealth Office staff and members of the military are often seconded to the palaces to advise the royal family on overseas visits and ceremonial matters, but there is not known to be a precedent for secondments from the royal household to the government.

A spokesman at Buckingham Palace said the Queen did not have any of her staff working in government on such an arrangement.

While Charles has previously been accused of using his position as the heir to the throne to lobby government, this is the first evidence of his potential influence within it in areas where policy is being decided.

It is particularly relevant at a time when Charles is taking on more of the Queen’s duties. In November he will step in for the 87-year-old monarch at the Commonwealth heads of government meeting in Sri Lanka.

Last week it emerged that the prince has held 53 private meetings with government ministers since the last election, including 36 with members of the cabinet.

Business sources said individuals were sometimes seconded from the private sector to provide expert assistance for a Whitehall project and it seemed unlikely the prince’s staff could provide such a service.

The Sunday Times established that an employee who was sent to Defra in January 2012 worked in a rural policy team, but the department would not give details of what issues the Clarence House staffer worked on or say whether ministers were told.

“It’s complete and utter news to me,” said one former Defra minister.

Charles has supported a badger cull, which falls into Defra’s remit. He is also known to be opposed to developing green-belt land and is against the introduction of GM crops.

The prince has a passionate interest in rural affairs and has established the Foundation for Building Community to preserve rural communities, but he also has commercial interests through the Duchy of Cornwall, which last year provided him with an income of £19m (Dh109m). Defra said the seconded staffer “would not have been involved” in any issues relating to the duchy.

A “junior official” from Charles’s staff is also understood to have been seconded to the Cabinet Office where she worked on “community-based things” such as the big society project, David Cameron’s flagship political initiative.

She is believed to have worked in the team of Nick Hurd, minister for civil society, whose brief includes charities and enterprises, such as the Prince’s Trust youth charity.

It is not known if Hurd knew she was on the prince’s staff, or that another seconded employee worked for the office for six weeks.

Sources close to Nick Clegg, who as deputy prime minister is in charge of constitutional affairs and issues relating to the monarchy, said they did not believe he knew of the secondments.

Paul Farrelly, Labour MP for Newcastle-under-Lyme, said on Saturday he would raise the matter with ministers as soon as MPs return from their 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.”