The News understands the Pompey defender is on the Championship outfit's summer wish list.
Whatmough is out of contract at Fratton Park and is currently exploring his options despite being offered fresh terms – something the Blues are doing, too, as they step up their efforts to find a suitable replacement.
Having recovered from a third serious knee injury of his career, the centre-back was a key player for Pompey this season.
He scored twice in 38 appearances as the Blues narrowly missed out on the League One play-offs.
Despite Danny Cowley currently overseeing a major overhaul ahead of a renewed promotion push next term, Whatmough is someone the head coach firmly wants to keep hold of.
However, a chance to finally test himself in the Championship is a reason why Whatmough could finally depart his boyhood club.
And it's understood that Luton are one side who are interested in his services and tempted to lure him away from Fratton Park.
Andy Awford, who gave Whatmough his Pompey debut when caretaker boss in November 2013, is academy and development manager at Kenilworth Road.
The Hatters are in the market for a central defender, having already lost Matty Pearson to Huddersfield at the end of his deal.
Sonny Bradley was also linked with a move to Ipswich but is reportedly now set to pen a new deal, but ex-Pompey defender Martin Cranie could depart.
Should the 24-year-old leave, Paul Downing and Sean Raggett will remain as Pompey’s only recognised centre-back options.