The East 17 singer — who is known to have experienced mental health problems — interrupted a live broadcast by the BBC from outside London's High Court.
Harvey, 48, is reported to have shouted loudly at the Duke Of Sussex as he arrived outside the building.
A BBC journalist tweeted: "So, turns out the protester who disrupted our live broadcast... Was Brian Harvey from E17! No wonder I lost my train of thought!"
So, turns out the protester who disrupted our live broadcast... Was Brian Harvey from E17!
No wonder I lost my train of thought! pic.twitter.com/YXJPck0kym
— Joe Inwood (@BBCJoeInwood) June 7, 2023
The Stay Another Day singer was pictured brandishing a giant copy of an email from a News Of The World journalist to the police, purporting to contain transcripts of conversations between Harvey and an alleged drug dealer in 2002.
Harvey was arrested on drugs charges in 2002.
The former boyband star — who appeared briefly on the fourth series of I'm A Celebrity... Get Me Out Of Here! in 2004 — claims he was a victim of phone hacking by tabloid journalists.
Harvey has made a lengthy post about his claims on his YouTube channel.
The pop singer has a history of mental health problems.
In 2021 he live streamed his own arrest on suspicion of sending a malicious communication.
In October 2014 he was filmed outside Downing Street demanding to speak to the then Prime Minister David Cameron about royalties he believed he was owed for East 17 Christmas Number One Stay Another Day.
The 1994 hit — on which Harvey performs lead vocals — was written by East 17's Tony Mortimer and co-writers Rob Kean and Dominic Hawken.
In 2005 he was treated in hospital after he accidentally ran himself over. Harvey fell out of the driver's door of his Mercedes and was run over by the vehicle, fracturing his pelvis in seven places, breaking his ribs and puncturing his lungs.
He later claimed he had eaten a large meal of three baked potatoes with cheese and tuna mayonnaise and had leant out of the door to be sick.
Prince Harry is currently appearing at the High Court as part of his trial against Mirror Group Newspapers (MGN).
The Duke is bringing a claim against MGN for unlawful information gathering, and has alleged that, amongst other things, employees of the publishing company hacked his phones and those of his associates and hired private investigators to illegally ‘blag’ his confidential information.
MGN have denied these allegations, instead insisting that some of the stories were sourced from within the royal households. However, they have admitted one article from 2004 about Harry’s visit to Chinawhite nightclub in London was the product of UIG.
Watch: Brian Harvey live streamed his own arrest in 2021