Southampton have asked the Premier League to investigate an alleged illegal approach from Liverpool for Virgil van Dijk.
It is understood that Southampton are yet to receive any contact from Liverpool regarding Van Dijk, despite the defender apparently indicating he is eager to move to Anfield.
Jurgen Klopp has made Van Dijk his top target this summer but Saints have been irritated by what they see as an attempt to unsettle their player and are ready to reject an official offer.
Liverpool may now face an ever-tougher battle to secure the 25-year-old, who has become one of the most sought-after defenders in the league since moving to the south coast from Celtic less than two years ago.
Last month, Southampton chairman Ralph Krueger told Press Association Sport the club could turn down even a £60million bid for Van Dijk.
"Can we? Yes," Krueger said. "We do not need to sell any player for the first time since I've been here."
Van Dijk signed a six-year contract 11 months ago but made only 21 Premier League appearances last term after missing the second half of the season with an ankle ligament injury.
The Dutchman is the latest in a long line of Southampton stars to catch the eye of Liverpool, who have signed Sadio Mane, Nathaniel Clyne, Rickie Lambert, Adam Lallana and Dejan Lovren from St Mary's, all in the last three years.