The member for Newcastle-upon-Tyne East, who has previously served as Labour chief whip, said a complaint has been made against him, the nature of which is unknown.
It is understood Mr Brown has been administratively suspended from membership of the Labour Party while an investigation is carried out.
This leads to the automatic precautionary suspension of the whip.
In a statement issued to the PA news agency, Mr Brown said he is not aware what the complaint refers to, but he is “committing fully” with the investigation.
“There has been a complaint made about me to the Labour Party which is under investigation,” he said.
“I am therefore under an administrative suspension from the Labour Party until the investigation is concluded.
“I’m not aware of what the complaint is. I am cooperating fully with the investigation.”