BBC political editor Nick Robinson says he regrets stamping on an anti-war protester's sign after an outside broadcast on the News at Six.
Robinson grabbed the sign, which had been in the background of his report from Westminster, and ripped it up.
"Apparently you can watch video of my sign rage in full glorious technicolour on the web," he wrote on his blog. "I lost my temper and I regret that."
He cared "passionately" about being able to do his job, he said.
"As I explained afterwards to the protesters who disrupted my broadcast, there are many opportunities to debate whether the troops should be out of Afghanistan without the need to stick a sign on a long pole and wave it in front of a camera," he said.
He said he was "a great believer in free speech" but that he also cared "passionately about being able to do my job reporting and analysing one of the most important political stories for years".
The incident is captured on a video that has appeared on web sites including YouTube.
After the incident, Robinson is shown telling a protester: "I'm not remotely ashamed of myself.
"Why should I be ashamed of myself?"