David Hearn, a three-time US Olympian and canoeist, has been indicted by a grand jury in Washington DC after Donald Trump blamed vandals for damaging Washington’s reflecting pool following a $14.7m renovation project.

The ‌indictment accuses Hearn, 67, ‌of “maliciously” breaking or destroying lining material on the bottom of the reflecting pool on 19 June. Lawyers for Hearn denied ‌the allegations following his arrest, accusing the ​Trump administration of treating ordinary conduct as criminal.

Jeanine Pirro, the US attorney for Washington DC, announced the single felony charge against Hearn at a press conference on Thursday, claiming prosecutors had “tremendous evidence” that the Olympian had “forcefully and violently” pulled up and removed the bottom liner in the reflecting pool. According to Pirro, Hearn was “belligerent” and “disrespectful” when asked to stop by employees of the National Park Service.

“Today is about accountability for damaging a national resource, a national treasure,” she said.

In a statement, Norm Eisen and Mary Dohrmann, lawyers representing Hearn, said he was innocent.

“These charges are outrageous and should be alarming to every American,” they said. “On the eve of our nation’s Independence Day, Americans should be deeply concerned by the misuse of government power against an ordinary citizen based on a concocted narrative.”

The US president ordered a vast renovation to turn the site “American flag blue” in time for the country’s 250th birthday celebrations this weekend. Only days after its completion, however, an algae bloom turned the water green.

Trump has alleged that a 300ft “gash” was cut through the sealant installed by contractors during the renovation. While the president claimed the US federal government would make public photographs and video to substantiate his claims, no such evidence has yet been released.

Hearn was arrested last month on a misdemeanor charge of destruction of government property, after noticing a partly detached piece of the blue liner and reaching into the water to see what it felt like.

“I didn’t vandalize anything,” Hearn, who had been cycling, told the Washington Post the following day. “I didn’t destroy or break or peel anything. By the time I realized what was going on, I was being put in handcuffs.”

At the time of his arrest, Hearn had just finished a 52-mile bike ride when he visited the Lincoln Memorial to see the refurbished reflecting pool.

The pool, built in 1922, runs more than 2,000ft between the Lincoln Memorial and the Washington Monument. Martin Luther King Jr delivered his I Have a Dream speech in front of the reflecting pool in 1963.

Trump had previously claimed the renovation he ordered of the site would be far more successful than those which took place under other presidents. His administration awarded a no-bid contract to a company Trump said had previously done work on swimming pools at one of his golf clubs.