The Oxford defender insists the worrying trend of violence towards players has to be stamped out quickly after a series of recent flashpoints.
A teenager has been charged after three Nottingham Forest players were allegedly assaulted while celebrating a goal during their 4-1 FA Cup win over Leicester.
Nottinghamshire Police said Cameron Toner, 19, of Leicester, has been charged with three counts of common assault and a separate offence of going onto a playing area at a football match.
Rotherham also banned two supporters for life earlier this month after a pitch invasion where Harry Pell appeared to be struck as he prepared to take a penalty against Accrington, with Stanley manager John Coleman saying he expected the game to be abandoned.
Leicester have also promised to issue a lifetime ban and Mousinho would support blanket bans for offenders.
He told the PA news agency: “I can’t see a reason for a fan to be allowed back into a football stadium if they come onto the pitch and assault a player.
“It’s a conscious choice. The term has to be large enough for people to decide they are not going to do it.
“Where fans come on the pitch, especially where there is an interaction with players, the harshest possible ban and consequences from a football point of view and a legal standpoint are needed, we would encourage that.
“From a players’ union view, when fans come on the pitch the players’ first instinct is to protect themselves. The guideline is for players to stay away but if someone is running at you, you don’t know if they are coming for a selfie or if they have a knife.”
Last month, Lucas Digne and Matty Cash were struck by a plastic bottle celebrating Aston Villa’s winner at Everton, while Chelsea’s Antonio Rudiger was hit by missiles thrown from the crowd in their 2-0 win over Tottenham.
Chelsea’s Sam Kerr was booked for pushing a pitch invader in the women’s Champions League match against Juventus in December.
In 2019, Jack Grealish was assaulted by Paul Mitchell after the Birmingham fan ran onto the pitch and punched the then Aston Villa captain at St Andrew’s. Mitchell was sentenced to 14 weeks in prison.
The PFA work with the Football Association and the leagues to ensure player safety but Mousinho feels security does need to be reviewed.
He said: “The easy reaction is to say the onus should be on clubs and the police but you have to qualify that and say we know the police have an incredibly difficult job.
“It’s a resources issue as well. There are only so many police and stewards who can be at grounds. Fans have to take some responsibility, we don’t want to have a situation where we’re banning alcohol from grounds. We don’t want to take draconian measures because it’s still a minority of people.
“There’s a collective responsibility. We have all been to grounds where lip service is probably paid to security.
“I’m not saying that’s right or wrong but you have security guards who don’t pat you down properly, I’ve been to Premier League grounds where the metal detector has gone off and nobody really cares.
“That’s a real concern and it’s never really been flagged before because most of the time, if you get a pitch invader, there’s a jovial atmosphere around how many stewards they can evade.
“Now there’s an aspect of violence which is really worrying. It’s really shocking and concerning. Hopefully it’s an isolated few weeks in an isolated season but it’s something we need to get on top of very quickly.”
Mousinho, who replaced Ben Purkiss as chairman last year, is also worried fan behaviour could push families away from the game.
The 35-year-old was at last summer’s Euro 2020 final where fans charged fences and 2,000 ticketless supporters entered Wembley ahead of England’s penalty defeat to Italy.
A Government report by Baroness Louise Casey found severe injuries or deaths could have been caused, with drug and alcohol use evident among fans.
“You are driving fans away, especially children,” added Mousinho. “There was absolutely no way I would have wanted my wife and kids to have been there, I would have gone straight home.
“The more we have of that, fans attacking players on the pitch and throwing things onto the pitch, the less appealing football will become to the wider audience.
“I’ve seen a lot recently surrounding the culture of drinking and drugs, drugs especially having a huge part to play in fan behaviour and, culturally, it’s possibly starting to get out of hand. The first step is to be aware of it and acknowledge we have a bit of an issue.”