England Under-21 manager Aidy Boothroyd said the task of developing players for the senior team and at the same time being expected to win trophies makes his job "utterly impossible".
England have lost their opening two games at the Euro Under-21 Championship and need to beat Croatia in Koper later on Wednesday, and hope Switzerland lose to Portugal, to have a chance of reaching the quarter-finals.
England have moved beyond the group stage only once in the last five editions of the tournament and Boothroyd said the way the international set-up was structured hampered their chances.
"I know the England senior men's job has been called the impossible job; I think the England Under-21s job is the utterly impossible job," he said.
"I say that because of the amount of players that have to be produced for the senior team and the fact we are expected to win.
"There's a reason we haven't won this for 37 years and why we haven't progressed as much as we thought we would. Part of that is because our primary aim is to get players through to Gareth (Southgate) and that's what we've done."
Boothroyd said he had hoped to have the likes of Jude Bellingham, Mason Mount and Phil Foden at his disposal in Slovenia, but that the senior team was always the priority.
"Could you imagine a reserve manager asking a senior manager for their best players to win the reserve league?" he said. "That just wouldn't happen.
"My job isn't to ask for Jude, Phil or Mason; it is about the senior team and always will be. If someone is keeping players here then the system is flawed, but it isn't flawed because we get players through."
(Reporting by Arvind Sriram in Bengaluru; Editing by Peter Rutherford)
