Ferdinand's absence from the 23-man squad that flew into Krakow on Wednesday evening has been a major talking point since manager Roy Hodgson chose to replace injured defender Gary Cahill with Liverpool youngster Martin Kelly on Monday.
"We're here to talk about the tournament, about the 23 players who are here and I'm not prepared to discuss - at all - any players who are not here," Bernstein said.
"It might be an issue - but it's an issue I'm happy to talk about when the tournament is over maybe. We are here to talk about the tournament and about the future and that's it.
"We all want to maximise our chances of doing well and we want to focus on what's ahead of us - not what is behind us.
"We'd hope you would join us in that, looking forward to do the very best we can with positive thoughts and not dwelling on all these sort of what are now frankly historical, extraneous issues."