The full extent of Liverpool's courtship of Southampton defender Virgil van Dijk has been revealed and now Chelsea could be next to stand accused of making an illegal approach for the Dutch defender.

A report on Yahoo Sport revealed that Klopp had shared video clips and taken part in detailed tactical discussions between Reds boss Jurgen Klopp and the Dutch defender, who had agreed terms over a move to Liverpool even though his club had not given any permission for talks to take place.

Southampton lodged an official complaint with the Football Association as they accused Liverpool of 'tapping up' their defender earlier this week, with an apology quickly posted by the Anfield club as they were forced to make an embarrassing public climbdown.

Sources close to Southampton have told Yahoo Sport that Klopp and Van Dijk have been in regular contact in recent months, even though they have not been given permission to speak to each other and no official offer has been made for the player.

The well-sourced report reveals one on one meetings between Klopp and Van Dijk have taken place, with personal terms already agreed between Liverpool and the player.

Video messages of tactical plans for next season were discussed, while the report also suggests Southampton believe Van Dijk's agent has been urging his client to join Liverpool as it meant he would receive more money as part of the deal.

"The club had to take a stand this week as we have been aware of what has been going on for months and it has gone too far," a source close to Southampton told Yahoo.

Southampton have told the player that we don't want to sell him this summer, but he thought he could kick up a big enough of a fuss and he would be sold for £50m.

"That is never happening and by holding talks with the player, sending him video clips of how he will fit into the their team and doing this all without the permission of Southampton, they is no way he will be sold to Liverpool at this stage.

"Of course, every player has a price and if £100m or something close to that is put on the table, then it will be considered, but Southampton don't need to sell Van Dijk this summer."

Southampton are now adamant that they will not sell Van Dijk to Liverpool after the illegal approaches to their player, with Chelsea also believed to have staged detailed talks with the defender without the permission.

Saints are now looking into the levels of contact between Chelsea officials and Van Dijk before considering their next move, with the defender now left in limbo after he made it clear he wants to leave the club despite having five-years left to run on the contract he signed only last summer.

A possible complaint to the FA over Chelsea's approaches for Van Dijk is being considered, with Southampton now 'more determined than ever' to block any move for the player unless 'silly money' is offered in the coming weeks, a source close to the club told this website.

That figure is believed to be in excess of £70m, which may well be enough to fend off interest in all interested parties.

A decision on Van Dijk's future is being complicated by the imminent change of manager at Southampton, with Independent.ie being informed that manager Claude Puel will be sacked after just one season at the Saints helm.

Online Editors