Norwich have had a bid accepted for Leeds midfielder and captain Jonny Howson.
The npower Championship confirmed they had "reluctantly" accepted an offer for the 23-year-old, whose deal at Elland Road expires in the summer.
A statement on the club's website read: "The club has reluctantly accepted the offer on the basis that the player only has six months of his current contract remaining and has expressed a desire to play Premier League football at the earliest opportunity."
Howson has been out of action since December because of a knee injury, and Leeds revealed their disappointment at not being able to tie the former England Under-21 international down on a longer deal.
"The club has been in discussions with the player about a new contract at Elland Road for more than 12 months, but he has been steadfast in his position that he would like the opportunity to play Premier League football," the statement continued.
"On that basis Jonny hasn't felt in a position to commit himself to Leeds United at this moment in time.
"The player would be able to leave on a free transfer at the end of his current contract.
"While accepting the offer on Tuesday the player has still to agree terms with Norwich and we are disappointed the matter has become public at this stage."
Norwich signed Bradley Johnson on a free transfer from Leeds in the summer after the midfielder's contract with the Yorkshire club had expired.
Lambert masterminded back-to-back promotions from League One after taking over at Carrow Road, with many of the current squad having come up through the divisions.
Like Johnson, summer signings Steve Morison, Anthony Pilkington and Elliott Bennett have all made a successful transition into the top flight.
The Norwich boss, though, admitted he was unsure how many more times he could tap hungry talent from down the pyramid.
"The lads we've got at the minute came from the lower leagues and the Championship, as everybody knows. I'm just not sure how many are left out there to go and find," Lambert said.
"The group need a hand and this is a huge season for the football club.
"We want to stay in the Premier League and get more finances from it and that's the reality of it.
"I'll do everything I can to get people in, but if not I'll go with the group I've already gone with."