From Longman Dictionary of Contemporary EnglishI must sayI must say (also I have to say)EMPHASIZE used to emphasize what you are saying The cake does look good, I must say. I have to say I was impressed. → say
Examples from the Corpus
I must say• I was pleased to find out, I must say.• The first day of my trip is now completed, and all in all, I must say I am quite satisfied.• When I did find out what he was thinking, I must say I was surprised.• Though, I must say, mediocrity never looked better.• Tell me more of it ... I must say my thoughts to you.• And I must say, on what I see, your methods seem to work well.• And first I must say why I need to make this digression. 