Nations League: England v Czech Republic in Prague on a Friday 'a concern' for FA
England's Euro 2020 qualifier against the Czech Republic being played on a Friday night in Prague "is a concern", says the Football Association's head of security Tony Conniford.
Some England fans clashed with riot police and Portugal supporters on two nights of trouble before the Nations League game against the Netherlands.
Conniford said: "I don't think these individuals worry about sanctions.
"Prague on a Friday night - I am not confident about that."
Conniford called the behaviour of some England fans in Portugal "a real disappointment" that left him feeling "embarrassed".
England travel to Prague on 11 October for the 19:45 BST kick-off and Conniford added: "Prague is a well-known city for welcoming stag dos. I think it has tried to change that image a bit over recent years but that is a concern for me.
"Perhaps, moving forward, when draws like that are made, like we do in England, if there is a potential issue then perhaps the authorities need to look at that and say, 'is England travelling to the Czech Republic on a Friday night the best thing for the game?'
"I want genuine people to come and everything was laid on for this to be a special event and unfortunately what we saw the other night deeply embarrassed me as an Englishman and didn't bring us any favours.
"So, there is a balance - I desperately want people to enjoy themselves."
There were believed to be 15,000 England supporters in Portugal and around 500 attended Wednesday's game at Porto's Estadio do Dragao which saw the home side beat Switzerland.
Some fans stayed in Porto, which is 30 miles away from Guimaraes and where England were beaten by the Netherlands.
The FA said they were "not true England supporters" and an "embarrassment to the team".
Conniford added: "For me, it has been a real disappointment because I asked the supporters to come here and respect the country.
"How many thousands of English people come to Portugal on their holidays and think about every single detail to make it pleasurable?
"A group decided they weren't going to do that and that's really sad.
"I don't think many of them are members. I don't think many of them want to be members.
"I think it's fashionable at the moment to follow the England team because success brings on many challenges and this is one of those challenges for us."