The white numbers, applied by a local company in New Zealand, failed to bond properly on the black jerseys and began to rub off during England's opening victory over Argentina.
Rugby World Cup Ltd have said they will be seeking assurances from England that there will be no repeat in Sunday's Pool B encounter with Romania.
A lack of clear shirt numbers breaches the tournament participation agreement.
It is not just fans and broadcasters who need clear numbers but also referees, touch judges and anti-doping officers in order to identify players.
An England spokesman would not confirm whether they plan to use the same printing firm this week, but he insisted they were addressing the problem.
"Nobody has contacted us yet. They know we will sort it out," he said.
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