US President Donald Trump has signed an executive order that he says will prevent future presidents from making certain changes to the White House Oval Office.

Trump, a former real estate mogul, has altered the president’s official office during his second term, most notably by adding many gold features to its walls.

“So we’re making it a national monument, and it will not be allowed to be touched by anybody, destroyed, ripped down by stupid people, in order to build something in a slightly different shape,” Trump told reporters on Thursday.

American presidents currently have the power to make some changes to the White House but large projects require the permission of Congress.

Thursday’s executive order declares the Oval Office to be a national monument, along with some of its surrounding rooms.

The document also says that it does not “restrict the President’s authority to redecorate the monument, select furnishings, or make ordinary operational and security modifications that do not substantially impair the monument’s historic structure or architectural character”.

“We like the Oval Office, and it’s a symbol like the White House itself. It’s a symbol of our country and the greatness of our country,” Trump said.

The president has the power to create national monuments, which are similar to national parks.

Trump’s order calls on the office to be maintained by the National Park Service “in a manner that protects its historic character, architectural integrity, and association with the Presidency”.

The entire building is already designated as a National Historic Landmark, which is intended to prevent against sudden changes to the building.

Trump’s proclamation notes the existing protection, but says “nonetheless, the Oval Office merits specific recognition and protective management as a discrete historic structure of national significance”.

Congress has carved out an exemption to the National Historic Preservation Act, in order to allow presidents to make needed changes. The current Oval Office has existed since the early 1930s, after its conception by President Franklin D Roosevelt.

Greg Werkheiser, from the law firm Cultural Heritage Partners, which specialises in historic preservation, says that temporary alterations like “furniture and decor is completely up to the president’s discretion”.

“As long as they’re not damaging the permanent art and architecture, they can generally do whatever they want,” he tells BBC News.

Werkheiser argues that the Trump administration has shown extreme disregard for other historic sites in Washington, and through lawsuits has attempted to undermine the laws that require preservation.

Trump has undertaken a massive beautification project in Washington and has held three events in the past week to boast of the construction, even as his Republican party was trounced by Democrats in the midterm elections.

“The hypocrisy is that on the one hand he’s talking about the importance of preserving the Oval Office – which is legally meaningless because he can’t do it – and on the other hand he is absolutely taking an axe to the law that allows us to preserve other historic sites.”

Werkheiser notes Trump’s efforts to renovate the Kennedy Center in Washington DC, to build a new triumphal arch in the city, and to paint the granite exterior of the historic executive office building. His firm has filed lawsuits to block two of the projects.

In October, the president suggested in an interview with Time, external magazine that the Oval Office would need to be torn down due to security concerns from the US Secret Service.

“I said, ‘My ass, you can’t build a new one. This is a special place,'” Trump said at the time.

During the midterm election campaign Democrats criticised Trump’s redesigns, with former President Barack Obama saying that his golden tweaks have “got the White House looking like Saddam Hussein opened a Cheesecake Factory”.