Prince Charles should not have staff working in the civil service if he believes in "royal political neutrality", a prominent Labour MP has said.

MPs are to raise the matter in the House of Commons after it emerged that two aides working for the heir to the throne have been seconded to two Whitehall departments.

One was sent to the Cabinet Office for two years, while another worked in the Department for Environment, Food and Rural Affairs for 14 months.

According to the Sunday Times, some of the ministers working in these departments did not know about the appointments.

Paul Flynn, Labour MP for Newport West, said the secondments suggested the prince was a "constitutional crisis in waiting".

"Planting his civil service moles proves [an] intention to abandon royal political neutrality," he said.

Paul Farrelly, Labour MP for Newcastle-under-Lyme, said he wanted an explanation as to why this had been allowed to happen.

"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."

It comes as MPs prepare to examine the prince's role in helping to shape government legislation.

Next month the Commons political and constitutional reform committee will examine the his little-known royal veto over new laws that affect his private interests.

It is also expected to look at recent revelations that the prince has held 36 meetings with ministers since the government took power in May 2010.

The prince has met David Cameron seven times, local government ministers four times and energy ministers six times.

A Guardian investigation in 2011 looked into the secretive constitutional position held by the prince that means ministers have been forced to seek his permission to pass at least a dozen government bills.

The Commons committee, chaired by Graham Allen, a Labour MP, will ask whether there is a risk that the requirement of royal consent "could be seen as politicising the monarchy".

Later this year the court of appeal will hear the latest stage of an eight-year battle by the Guardian to get the government to reveal a set of 27 letters written by the prince to ministers in seven departments over a nine-month period.