Mark Catlin has urged the Fratton faithful to help ‘self-police’ the individuals threatening to ruin Pompey’s reputation.
Several isolated cases have recently drawn negative attention towards the Blues’ fanbase.
These have included a pyrotechnic dropped into Sunderland’s family section, social-media racism directed towards Peterborough’s Ivan Toney and abusive phone calls to Ronan Curtis.
As a consequence of last month’s smoke bomb incident at the Stadium of Light, Pompey’s ticket allocation has been reduced from 3,222 to 2,000 for Saturday’s play-off semi-final first leg.
Catlin is at pains to stress a tiny minority of Pompey fans are responsible, with ‘99.9 per cent’ well behaved.
But the Blues’ chief executive has vowed not to let them tarnish the Blues’ good standing.
He said: ‘I will stand behind Portsmouth fans, they are one of the most passionate, loyal, brilliant fanbases in the country.
‘I am not going to let a few idiots spoil that reputation. I’m not going to allow the minority of people spoil what I believe is the reputation for the majority.
‘Unfortunately there have been a few incidents occurring recently.
‘But if there is any silver lining, it is the huge backlash from Pompey fans – who I consider the vast majority – towards such culprits.
‘You want our fans to self-police to a degree so that things become socially and morally unacceptable, maybe they become isolated.
‘The last thing anyone wants is for a Pompey fan to get into trouble with the authorities.
‘I don’t want to highlight the incidents, they have been caused by one or two individuals.
‘You don’t want to keep publicising, it’s not representative of the vast majority of Pompey fans who are decent, want to go to a game, want to enjoy it, want to get home safely and don’t want to cause any trouble.
‘I am loath to keep going on about individuals, but it’s just that, individuals.
‘You can’t say and use the word “Pompey fans” for the actions of a few mindless individuals.’
Kenny Jackett’s side now find themselves in the League One play-off semi-finals.
The first leg is at Sunderland on Saturday, May 11 – and Catlin is hoping there will be no repeat of the pyrotechnic issue from last month.
He added: ‘I hope our fans behave, whether it’s against Sunderland or any other team, and it’s important to note that 99.9 per cent of them do.
‘Having said that, I’m reading all too frequently lately of mainly individuals doing something which unfortunately tarnishes the whole fanbase – and that’s really upsetting.’