Cortese told BBC Solent: "We were in a similar position to the likes of Norwich and Charlton.
"We started with minus-10 points but now we're 31 behind Norwich, and 22 behind Charlton. The gap is too much."
Cortese was responding to questions from supporters, in an exclusive interview broadcast on BBC Radio Solent.
The Italian former banker arrived at St Mary's in August last year, following Markus Liebherr's purchase of the club.
Last month Cortese commented publicly that league results "needed to improve", with Southampton having invested heavily in the likes of Rickie Lambert, Lee Barnard and Jose Fonte.
Source: BBC Sport
Source: BBC Sport