The comments come in the wake of the news that England are looking to call up Brad Shields to the England team once he moves to Wasps at the end of the season.
Shields only qualifies for England through his parents and has lived in New Zealand for his whole life, as he prepares to depart Hurricanes after six years at the club.
And Johnson says it is a worry that England have to search for players in other countries rather than produce their own.
"We should be producing more top-end players," Johnson told The Times. "I don't know what the answer is. There's more people employed in developing rugby talent in this country than ever before - so why is it not coming through? It is a concern. We don't seem to have the depth.
"Who's this guy they're signing from New Zealand?
"My answer is: there's a reason they're doing it [bringing in Shields]. This has been coming for a while. Eddie's doing it because he obviously doesn't think he's got enough talent in England."