In the English Grammar Profile, B1 point 72 in the category of MODALITY is defined:
the fixed expression: ‘I have to admit’ for emphasis
PELIC STUDENT EXAMPLE:
When I want to talk about my weaknesses in writing in English,
I have to admit the new words are my main problem.
Arabic male, level 4 writing class.
TLC STUDENT SPEAKING TEST EXAMPLE:
Therefore, I have to admit that it’s true with most old people,
but with my parents,
I think that before I was born they hoped that they were going to have a girl.
male China C1
*There are only a few examples that all start at C1 in the TLC.