Southee took seven for 33 in his nine overs as England collapsed to 123 all out in just 33.2 overs.
New Zealand captain McCullum’s rollicking 25-ball 77 with seven sixes and eight fours at the top of the order then saw the tournament co-hosts romp to victory in just 12.2 overs of their reply in Wellington.
When the umpires called for a dinner break with New Zealand needing just 12 more runs to win, jeers rang out around the packed 33,000 capacity Westpac Stadium.
But although the amount of cricket played was under half the scheduled 100 overs of a one-day international, the crowd certainly got their money’s worth.
Victory gave New Zealand, one of the tournament favourites, their third win in as many Pool A games while England were left with two defeats in two following a 111-run thrashing by Australia.
Sensing an easy win, McCullum launched a ferocious attack on the England bowling, hitting Stuart Broad for a six off the first ball he faced.
Fast bowler Steven Finn was not spared as McCullum hit six, four, four and six off the Middlesex paceman’s first four balls and then another six to bring up his fifty off just 18 balls.
McCullum held the previous record for the fastest World Cup fifty, off 20 balls against Canada at St Lucia in 2007.
Finn’s two wicketless overs cost a whopping 49 runs
Chis Woakes ended McCullum’s knock by bowling him off a bottom edge.
South Africa’s AB de Villiers holds the record for the fastest-ever one-day international fifty, off just 16 balls, made against the West Indies last month.
Earlier it was Southee who left England clueless after Eoin Morgan won the toss and batted on a flat looking pitch.
Southee achieved the third-best figures in all World Cups and beat the previous best by a New Zealander in all ODIs, recorded by Shane Bond, now the team’s bowling coach, who took six for 19 against India at Bulawayo in 2005.
Only Joe Root, last man out in the 34th over, offered resistance with 46 while opener Moeen Ali made 20 and Morgan managed 17 in an otherwise disappointing batting display.
“It’s a bit of a blur at the moment,” said Southee during the change of innings. “We’re good swing bowlers and, although we lost the toss, the ball swung throughout the innings.
“They say that when there’s a bit of blue sky in Wellington, the ball swings.”
England were looking at a revival at 103 for three with Morgan and Root at the crease.
But former Ireland left-hander Morgan, who had managed just two runs with four ducks in his previous five innings, holed out at long-on off Vettori.
He was left to rue his shot as England lost their last seven wickets for just 19 runs.
Openers Ian Bell (eight) and Moeen Ali (20) were both bowled by Southee, who subsequently dismissed James Taylor (nought), Jos Buttler (three), Chris Woakes (one), Stuart Broad (four) and Steven Finn (nought).
He took his final five wickets in the space of just 18 balls to record the third best figures in all World Cups behind the Australian duo of Glenn McGrath (7-15) and Andy Bichel (7-20).