The creature, which appeared large due to its position in the shot, dropped into the frame as the shadow chancellor was talking about economic growth.
It seemed to be on the camera lens and dangled above Mr Balls’ shoulder, quivering, with its legs moving.
It then moved so it looked from the viewer’s perspective as though it was touching the MP’s face, before quickly scuttling up and out of the shot.
It is not the first time a spider has hogged the limelight during a live news bulletin, as the BBC News (UK) Twitter account pointed out following the incident today.
In August, a spider invaded the early morning edition of Reporting Scotland when it crept across the lens of the roof camera to catch an insect.
Newsreader Graham Stewart looked unperturbed as the spider grabbed the insect before retreating.
He later tweeted: ‘’Never mind the pandas: giant hungry spider invades Reporting Scotland at breakfast time!’’
The clip drew widespread attention on social media, with more than 200 retweets on Twitter in just over an hour.