And, last night, they ensured the Blues even eclipsed that miserable landmark on another depressing Fratton Park night.
It was almost 11 years ago when the O’s inflicted a 4-1 FA Cup defeat on Graham Rix’s side at the same venue.
A 3-2 victory for Russell Slade’s men in the driving rain in front of just 9,955 fans last night was clearly not as comprehensive.
However, a seventh successive defeat means Pompey are now on their worst losing streak for 37 years.
Previously, Ian St John’s men endured nine on the bounce in the 1975-76 campaign – a season which would end in relegation to division three.
The current crop are spiralling in the same direction and, in truth, their latest blank was another deeply-disappointing affair.
Izale McLeod missed a penalty in the 27th minute during a woeful first half from the hosts, who headed to the interval 1-0 behind courtesy of Kevin Lisbie’s 32nd-minute strike.
Moses Odubajo doubled the visitors’ advantage before McLeod pulled one back from the spot in the 57th minute – ending the Blues’ run of 546 minutes without a goal.
Lisbie grabbed a second – this time from the spot – before Scott Allan responded in the 65th minute to make it 3-2.
It was an improved final 30 minutes from the hosts but Guy Whittingham’s men could not find the equaliser – even during five minutes of time added on.
As it was, it ended up being a miserable end to the loan spell of Mikkel Andersen, who now returns to Reading, and a disappointing return for Ricardo Rocha, who came on as a 35th-minute substitute.
More importantly, Pompey’s horrific run continues and those relegation concerns deepen.
With Carl Dickinson returning to Watford and Lee Williamson injured, Whittingham made two enforced changes to his team.
Jon Harley came in at left-back, having been on the bench for Saturday’s defeat against Doncaster Rovers.
In addition, Allan was available again after serving a three-match suspension and he was restored to the team on the right-hand side of midfield.
Meanwhile, Rocha was named on the substitutes’ bench after signing a month-long deal on Monday.
When the match got under way, the hosts were relieved to see Lee Cook’s fourth-minute free-kick from the right fizz through the area and just past the far post.
The slightest of touches would have seen Whittingham’s men slip behind so early in proceedings.
At the other end, a corner fell into the path of Nathaniel Mendez-Laing, who lashed a powerful half-volley which was destined for the net.
However, the ball instead cannoned off an unaware Gary Sawyer and bounced harmlessly clear.
David Mooney then had a golden opportunity to break the deadlock only to take a bad touch when clean through and Gabor Gyepes gratefully tidied up.
Pompey were rocking and, in the 14th minute, Martin Rowlands drilled a first-time shot from just outside the box narrowly past the post.
In the 26th minute the Blues were awarded a penalty when Ryan Allsop brought down Brian Howard.
McLeod took on the spot-kick duties but Allsop produced a brilliant stop – saving with his legs while off the ground – and the chance was wasted.
Barely a minute later, Orient were given a four-on-one situation during a swift counter-attack but Anderson managed a superb save to deny Cook.
In the 32nd minute the deadlock was broken, though.
A sublime ball down the middle from Dean Cox was flicked first time by Lisbie past the advancing Andersen and into the net.
In their next attack, Cox swung in a free-kick from the left which was met with a free header from Mooney only to flash narrowly wide.
Whittingham swiftly reacted by hauling Gyepes off and replacing him with Rocha on 35 minutes, much to the delight of the Fratton faithful.
Yet Pompey limped to the interval relieved they had not leaked any more goals as Orient continued to run them ragged.
At half-time, Pompey were sent out early for the second period by the caretaker boss, clearly an indication of his anger at the opening 45 minutes.
However, in the 51st minute they fell further behind when Odubajo shrugged off Howard and slotted the ball through Andersen’s legs and into the net.
Moments later, Allan just failed to thread the ball through to McLeod as the pair bore down on goal.
But in the 57th minute Pompey had their lifeline when Paul Benson nicked the ball off Nathan Clarke and the defender brought him down. This time, McLeod finished the penalty in clinical fashion and the deficit was one goal.
That didn’t last long, though, and when Lisbie was brought down by Rocha, the striker stepped up to net from the spot.
Still the goals flowed and in the 65th minute, Allan twisted and turned on the right-hand side of the box before drilling in a shot which was deflected into the net to make it 3-2.
Pompey pressed for an equaliser and Allsop did well to produce a smart reaction save to keep out substitute Johnny Ertl’s shot in the 85th minute.
Yet there was no stunning comeback and it was defeat number seven for the limping Blues as their depressing run continues.