McCartney joined Springsteen on stage for renditions of The Beatles' 'I Saw Her Standing There' and 'Twist and Shout' at the end of The Boss's 29-song set, which closed the Hyde Park festival's second day.
However, their performance was halted before they could thank the crowd after they broke the council's curfew.
Springsteen's guitarist Steven Van Zandt later took to Twitter to criticise the authorities for turning off the singers' microphones.
"One of the great gigs ever in my opinion. But seriously, when did England become a police state?" he wrote.
"We break curfews in every country but only English cops needs to 'punish us' by not letting us leave until the entire crowd goes. Is there just too much fun in the world? We would have been off by 11 if we'd done one more. On a Saturday night! Who were we disturbing?"
NME reports that a spokesman for event organiser Live Nation has defended the decision, saying: "It was unfortunate that the three-hour plus performance by Bruce Springsteen was stopped right at the very end but the curfew is laid down by the authorities in the interest of the public's health and safety.
"Road closures around Hyde Park are put in place at specific times to make sure everyone can exit the area in safety."
Springsteen was earlier joined by Rage Against The Machine's Tom Morello for two songs, as well as singer John Fogerty.
Hard Rock Calling wraps up today with performances by Paul Simon, Christina Perri and Guillemots.
Watch Bruce Springsteen and Paul McCartney at Hard Rock Calling below:
Click through our gallery of Hard Rock Calling 2012 below:
Copyright: PA Images Lewis Whyld/PA Wire