England centre Manu Tuilagi has been fined £4,800 by Rugby World Cup officials for wearing a sponsored mouthguard during the win over Georgia.
Tuilagi, whose brother Alesana was fined last week for the same offence, also wore the gumshield in the victory against Argentina.
The Rugby Football Union (RFU) said Tuilagi's breach was a "genuine error".
Meanwhile, Jonny Wilkinson, who has a niggling shoulder injury, took part in a light training session on Tuesday.
Wilkinson damaged his elbow against Scotland last weekend and manager Martin Johnson said on Sunday he was worried the injury would keep his star fly-half out of England's last-eight match against France on Saturday.
But concerns persist over centre Mike Tindall, who suffered a dead leg in Saturday's victory over Scotland and sat out training.
Fellow centre Tuilagi, who is expected to feature against France, said of his fine: "I didn't know I had worn the wrong gumshield and I got fined for it."
The 20-year-old insisted both he and his brother, who plays for Samoa, did not deliberately flout the International Rugby Board's strict advertising and sponsorship rules.
"We always wore the same mouthguard, mine is the England one from the under-18s, but it's not allowed in the World Cup," added Tuilagi, who has been in impressive form in New Zealand.
"I coloured it in with marker pen for the Romania game. I wore it against Argentina but they didn't know."
An RFU spokesman said England had not been fined for any other breaches during the tournament.
"Manu wore a mouthguard where the branding was visible in the Georgia match when it shouldn't have been so therefore he's been fined 10,000 New Zealand dollars," said the spokesman.
"It was a genuine error and he's trying now to focus on Saturday's game [against France]."