The 23-year-old, who came through the youth system at Dutch giants Ajax, was wanted by Nottingham Forest last summer.
He is now again on the radar of a Championship club and Millwall have made a move to tempt Fortuna Sittard into selling Flemming in this month’s transfer window.
Millwall have put a bid in for Flemming, however their €1.3m offer was judged not good enough, according to Dutch magazine Voetbal International.
Flemming is under contract at Fortuna Sittard until the summer of 2024 and the club are under no pressure to sell.
The Dutch club are involved in a relegation scrap in the Eredivisie and currently sit second bottom, three points from safety.
Flemming has made 13 appearances in the Dutch top flight so far this season, scoring twice and providing two assists.
All eyes will be on whether Millwall go back in with a fresh offer for the 23-year-old this month.