Dan Glass, a member of Plane Stupid, was about to receive an award from the prime minister when he stuck out his superglued hand and touched his sleeve.
Plane Stupid says Mr Glass, from north London, then "glued his hand" to Mr Brown's jacket as he shook his hand.
But Downing Street said there had been "no stickiness of any significance".
'Stick to promises'
Plane Stupid recently gained publicity by mounting a protest on the roof of Parliament.
Spokesman Graham Thompson said Mr Glass - a 24-year-old post-graduate student at Strathclyde University - had smuggled a small amount of glue through Downing Street security checks in his underwear at about 1700 BST. ...
Speaking afterwards, Mr Glass said: "My left hand was covered in superglue and I stuck it to his sleeve.
"I just glued myself to him and after 20 seconds he tore my hand off - it really hurt. He had to give it a couple of tugs before it came away.
"He was just grinning about it. He didn't seem to take me seriously."
After the incident Mr Glass was allowed to stay Number 10 for 40 minutes.
When he left the building he tried to glue himself to the gates of Downing Street but was prevented from doing so by a police officer.
"I didn't have much glue left by that point," he said. ... - bbc
Does someone want to explain to Americans what a "campaigner" is?