A war of words erupted between NBC Universal and Apple on Friday, laying bare the tension between media and technology companies as they fight for advantage in the burgeoning market to sell video online.

The two companies had been negotiating to renew NBC’s contract to sell its television programmes through Apple’s iTunes digital media store. However, the talks soured after NBC told Apple it would not renew the original deal because of frustrations about iTunes’ pricing policy and anti-piracy controls.