Goal.com exclusively revealed how the Welsh midfielder had been the subject of a £13.5 million bid from Liverpool, which has been accepted.
Allen is believed to be keen on a switch to the Reds to link up with former manager Brendan Rodgers, who was in charge of the Swans last season.
An agreement was rumoured to be in place whereby Rodgers would not be allowed to poach any of his old players for the first 12 months of his contract.
It has since emerged, however, that Allen has a clause in his contract stating that if any of five clubs (Liverpool, Manchester City, Manchester United, Arsenal and Chelsea) bid £15 million for his services, he may leave.
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The Swans statement read: “Swansea can confirm Liverpool have expressed an interest in Joe Allen despite a written agreement with Liverpool not to approach any players within the 12-month period of Brendan Rodgers leaving for Anfield.
“There has also been interest from other clubs and the club is due to speak to Joe about the situation when he returns from GB duty.
"The club is not prepared to release any details on whether any formal bids have been made at this stage or details of Joe’s contract.
“Fortunately the club is in a financial position where it does not need to sell any of its players."