Wales grabbed a very credible 0-0 draw in Russia on Saturday, meaning their Euro 2004 play-off is balanced on a knife-edge.
Mostovoi is suspended for the second leg in Cardiff, but he has attacked the Welsh for their actions at the weekend.
"Giggs and his fellow players were swearing at us from the first minute," said the Celta Vigo star.
"Almost all of them made ugly faces at us and used every opportunity to shout dirty swear words.
"It was very strong, 'f*** off' and worse abuse heaped on us from the dustbin.
"I can't speak for the rest of the boys, but for me the most unpleasant were Savage and Koumas.
"At one point Savage even stuck his finger in my face.
"For me it came as a big and unpleasant surprise. As a kid, I thought the British were real gentlemen."
