Preston are to report Championship rivals Watford for unsporting behaviour after a row over the multi-ball system at Vicarage Road last weekend.
North End manager Alan Irvine will complain to the Football League about the apparent gamesmanship of Watford groundstaff during his side's 2-1 defeat.
Irvine, who branded the antics of Watford's ball boys and other club personnel "disgraceful", will also claim extra footballs were deliberately thrown on to the field during the second half as Preston pushed for an equaliser.
Irvine - involved in a furious exchange of words with the fourth official - told the Lancashire Evening Post: "You are supposed to give the ball back at the same speed for both teams, but it was getting thrown back quickly for the home side and slowly for us.
"They also deliberately threw a ball on because they knew it was trying the patience of the referee. That is an absolute disgrace.
"That was a deliberate ploy. They knew that if an extra ball came on to the pitch on enough occasions then the referee would scrap it. They were winning 2-1. Who does that favour?"
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