The Prince of Wales is routinely shown plans for major building projects in London to avoid him raising damaging objections later on, developers have admitted.

The disclosure — a week after he succeeded in blocking plans by Lord Rogers of Riverside for Chelsea Barracks — will raise questions that the Prince is operating as an unaccountable planning authority, forcing developers to second-guess his wishes so that they do not face the possibility of ditching plans that have been years in the making. A report by Building magazine says that the developers behind the Battersea Power Station and the King’s Cross developments both checked plans with the Prince.

The practice emerged this week at the British Property Federation annual conference, when Robert Tincknell, managing director of Treasury Holdings UK, said of Battersea Power Station: “Yes, we have run our designs by Prince Charles.”

When contacted by Building, other developers said that they also gave the Prince a chance to look at their plans before going ahead. Peter Freeman, founder of the Argent Group, confirmed that the same had happened with the King’s Cross scheme. “The Prince has a big voice,” he said.

Land Securities, responsible for Rafael Viñoly’s controversial “Walkie-Talkie” design for 20 Fenchurch Street in the City, said: “Prince Charles has always been very vocal. He didn’t like 20 Fenchurch Street.”

Land Securities is believed to be one of a number of developers that routinely receive letters from Clarence House offering “opinion and advice” on the design of buildings.

A senior industry source told Building: “If the Prince sees a developer working on something big that he has an opinion on, he’ll write and present any criticisms. Developers don’t have to consult with him as a result, but they often do. I suspect the Prince can be very influential when it comes to development.”

David Roberts, deputy chief executive at developer Igloo, said that checking major schemes with Clarence House was accepted practice.

“I agree with a lot he says,” Mr Roberts said, “but it’s inappropriate that he has so much influence. It can’t be right.”

Other developers, including British Land and Heron, said that they had never run plans by the Prince.

The Prince’s early tussles with architects and developers involved him applying pressure through public pronouncements that garnered huge publicity, as in the “carbuncle” speech which succeeded in derailing plans for the National Gallery extension.

Now he is as likely to operate behind the scenes. In the Chelsea Barracks row, he wrote a private letter to the Qatari developers to get them to drop Lord Rogers’s master plan. Clarence House never publicly confirmed that he wrote the letter.

After he was dropped by the Qataris – who have agreed to consult Charles’s charity, the Prince’s Foundation for the Built Environment, in drawing up a new plan — Lord Rogers attacked his behaviour as unconstitutional and demanded that a panel of experts review his political influence.

While most constitutional experts said that there was nothing to prevent the Prince speaking out on issues that concerned him, some have raised fears that it could create problems for him later on. Bob Morris, of the University College London Constitution Unit, said: “There is a danger that the Prince may so establish in people’s minds a propensity to sound off or interfere that, on succession, an impartiality which will be – and will have to be – genuine may not be believed. The future for a compromised monarch may be uncomfortable.”

Clarence House said that it did not comment on private correspondence.

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