Manchester United have been told Sadio Mane would cost double what they offered to secure his services in the summer, according to the Daily Telegraph.
United were keen to sign the Senegal international during the transfer window and were prepared to pay around £20m to bring him to Old Trafford.
However, Mane's flying start to the season means Louis van Gaal's side would need to part with £40m to convince Saints to sell their star attacker.
United eventually spent big to bring in teenager Anthony Martial from Monaco on deadline day last month for a fee that could rise to £58m, but are still exploring the possibility of bringing Mane to Old Trafford.
Saints have made a stuttering start to the season, though Mane, 23, has played a crucial role for the south coast side having netted two goals and register a further four assists, which has contributed to his WhoScored rating of 7.53.
For more stats on Sadio Mane, click here to view his WhoScored player page
