Forshaw has been top of Uwe Rosler's summer transfer hit list for the duration of the summer and the 22 year old has been in town for talks today.
Mark Warburton, Brentford FC Manager, said: “We have stipulated from the outset that any deal involving our players will be done on our terms. A valuation was given and not met, hence the delay in proceedings.
“Now that our valuation has been met we have given permission to Adam to meet and talk with Wigan. Brentford did not need to sell Adam and we will not be dictated to by any individual or potential buying club in such situations.
“Why was Adam not considered for games thus far? Again, as we have clearly stated, we will only look to players who are absolutely committed to the Brentford cause and such events can only distract a young player and negatively impact his contribution.
“Now that this matter is near conclusion, I would like to wish Adam all the very best for his career and to thank him for his outstanding efforts over the last two years.”
The move is expected to be finalised in time for the former Everton player to face Birmingham City on Saturday.