London - Arsenal have been fined £60,000 and warned over their future conduct for falling foul of football agent rules in the transfer of Calum Chambers from Southampton, the Football Association has announced.
Agent Alan Middleton was fined £30,000 and suspended for three months for his part in the transfer.
Chambers moved from Saints to the Gunners in July 2014 for an undisclosed fee, believed to be in the region of 11 million.
An FA statement read: "Arsenal admitted part of the breach (of Football Agent Regulations) but denied another, which was found not proven following an Independent Regulatory Commission.
"The charges against Mr Middleton, which he denied, were found proven."
The written reasons for the sanctions described the incident as a classic case of "fronting", where an unauthorised and unlicensed agent was involved.
A statement from Arsenal read: "We acted in good faith throughout in this transfer and had no reason to believe that the player's representative was not authorised to be involved in the transfer negotiations.
"The FA fully recognised that there was no intention to mislead on Arsenal's part.
"We have improved our procedures to prevent this happening again."