Goal understands that the pair are set to move to St James' Park and Forest boss Pearce expressed his disappointment about how the deal had been done, albeit without any official confirmation from either club.
It appears that Lascelles and Darlow will be loaned back to Forest for the 2014-15 campaign but Pearce is unhappy about the size of the fee accepted for the two players.
"We had an offer from Newcastle, that I was made aware of last week, in regards to the two players going there," Pearce is quoted as saying by the Nottingham Post.
"The figures that were mentioned, by the representative of our club - I said I would not do that deal, when I was asked the question.
"I thought I could push their value up and that they would be worth more in the long run.
"The first I heard today [Monday] about things was when Jamaal Lascelles came in and told me that he had a medical at 2pm at Newcastle. That disappointed me greatly.
"I think I have a good relationship with the club. But obviously, for whatever reason, they have decided to take the money on this situation.
"I do not agree with it. But the only olive branch I have got is that the boys are both coming back on a year loan, which is a bonus.
"But I felt that, if they stayed at the club, they would only have increased in value."