The visitors raced into a 3-0 lead within 11 minutes of the kick-off, and eventually ran out deserved 4-1 winners after putting down a brief Magpies fightback.

But the home side were the architects of their own downfall as they gifted Pompey their second two goals and did little to prevent the fourth on a black afternoon at St James' Park.

Allardyce was in sombre mood as he surveyed the wreckage of a Barclays Premier League defeat which heaps further pressure on his team ahead of next weekend's derby trip to Sunderland.

He said: "Disappointed is an understatement - I am devastated by what has happened here today. I am completely gutted inside.

"What I put out on the field of play is an extension of me, it is what I am.

"The players have to go out and emulate that and put a performance on, be organised, understand how they should play, keep their shape, keep their discipline, use their abilities in the right areas, make sure they help their mate out if he has made a mistake and really go out and use their talents in the right part of the field.

"Unfortunately today, that did not happen. We lost all our discipline in the end and all our shape and organisation.

"Going chasing lost causes means you lose even deeper and harder and longer.

"We were our own worst enemy today. Portsmouth did not have to put us to the test because we gifted them the game in those 12 minutes."

Noe Pamarot blasted the visitors ahead with an eighth-minute piledriver, but hapless Brazilian Claudio Cacapa endured a personal nightmare as he was muscled off the ball by first Benjani Mwaruwari and then John Utaka as Pompey established a 3-0 lead before Newcastle had got their second wind.

Cacapa was put out of his misery when he was hauled off with just 18 minutes gone, and by that time, his side had grabbed a lifetime when Sol Campbell deflected the ball into his own net.

However, any hopes of a fightback died when Niko Kranjcar's 70th-minute free-kick eluded Steven Taylor, Abdoulaye Faye and then stand-in keeper Steve Harper to cement the win.

Allardyce said: "We lost the game in the shortest period of time ever since I have been here. That sums it up, basically.

"While you can work as hard as you want in the week and put as much into your players as you possibly can and look forward to playing at home where we have done so well and have played with so much confidence, it was all destroyed in a 12-minute period at the beginning of the game."

To make matters worse, Nicky Butt picked up his fifth booking of the season and will miss the Tyne-Wear derby, while Allardyce revealed keeper Shay Given is facing up to three weeks on the sidelines with a recurrence of his groin injury.

The 52-year-old's mood was in direct contrast to that of opposite number Harry Redknapp, who left the north-east celebrating a fourth successive Premier League victory on the road.

He said: "It was a terrific performance and great goals. The first three goals were fantastic.

"You come to St James' Park and it is a difficult place to come - they get great support - and I just felt it was important we did not give anything away early on.

"The system we play, we have got an extra man in the middle of the park and they were going to get out-numbered in there, so I felt it was important we passed the ball and made them change their system or drag a wide man in.

"That was something we spoke about all week, and we did it to perfection - and the goals were absolutely fantastic."