He has already been capped by England, but his appearance against Sweden in November 2012 was in a friendly and would therefore not prevent him from representing the nation North of the border.
McGhee has confirmed that the former Tottenham Hotspur centre-back is somebody that Scotland have been monitoring for some time, and have hinted that they will invite him to represent the Tartan Army.
"He's someone who does fit the criteria as I understand it," McGhee told reporters.
"We know who the boy is, we knew about him before he was at Tottenham. We're interested in looking at all players who meet the criteria."
Caulker moved to Cardiff from White Hart Lane in an £8m switch this summer.