Kieran Trippier told a friend to “lump on” over his 2019 move from Tottenham to Atletico Madrid, according to the Football Association.
The exchange was detailed in the written reasons for the FA’s decision to give Trippier a 10-week worldwide suspension for breaking betting rules.
The England right-back, 30, was also fined £70,000.
He was found guilty in December of four betting rule breaches, though his ban has been suspended pending an appeal.
Three other charges were dismissed by the independent regulatory commission that heard the case.
The written reasons published contained WhatsApp messages exchanged between Trippier and his friends, who placed a number of bets from £20 to £300 on the transfer to Atletico.
The commission rejected Trippier’s assertion that the messages were just “banter”.
One message from a friend, three days before the £25m move was completed in July 2019, asked: “Shall I lump on you going there?”
Trippier later said: “Lump on if you want, mate.”
The commission said: “We simply do not accept that these messages would be read by Kieran Trippier as ‘banter’.”
It added Trippier’s friend was “seeking reassurance” that he should bet heavily on the move and Trippier “provided such reassurance”.
However, in its conclusion, the commission added it had “no means of knowing the size of the bet placed” and that by “this time the odds on Kieran Trippier’s transfer were very short” as it was expected the move would take place.
The commission also found that the betting by another of Trippier’s friends in the charges that were proven “was comparatively modest in scale” and the defender’s “offending” in relation to these charges “was very much at the lower end of the scale in terms of his culpability”.
Trippier’s good disciplinary record, character and the remorse he showed were also factors in determining the sanction, the commission said.
The commission was provided with witness statements on behalf of Trippier from, among others, England manager Gareth Southgate, captain Harry Kane and his former manager at Burnley, Sean Dyche.