The statement, made just days after Tim Cobbold assumed the chief executive mantle at De La Rue, confirms its French rival has maintained interest in a bid.
Oberthur said the initial bid had taken into account this potential loss of work from the customer, believed to be the Reserve Bank of India, but added that it now understands that paper production problems last year had damaged that relationship and the work had been lost to rivals.
It said: "Oberthur believes that De La Rue should inform the market if it was an unsuccessful participant in such key tender for the Reserve Bank of India or if it was not even invited to participate in that tender.
"it is important for De La Rue to provide a full update to its shareholders as to its realistic prospects of obtaining new business from this very important customer.
"It remains Oberthur's wish to enter into substantive discussions with the Board of De La Rue, possibly leading to an offer for the company."
Adrian Kearsey, an analyst at Evolution Securities, said: "The timing of this is not surprising. They have a new CEO who only started 1 January. So they're turning up the heat to force them to the table to talk.
He added that despite De La Rue shares rising slightly on the news, this was a reaction to the news that Oberthur remained interested in pursuing a bid rather than to the likelihood of whether or not the company had kept Reserve Bank of India business.
"The market is assuming that the probability that De La Rue has not retained the contract is greater than the likelihood that they have," he said. "We're not surprised [at the Oberthur announcement] - we have assumed the chance of them losing the contract was quite high."
De La Rue responded in a statement saying that "as soon as this uncertainty [regarding the key customer] is removed, De La Rue will make an appropriate statement to the market".
De La Rue chairman Nicholas Brookes said: "Outside of the well-publicised paper production issues with a major banknote paper customer, which we first announced in July 2010, De La Rue continues to enjoy encouraging order levels which are at comparable levels to the equivalent period last year."
Oberthur corners De La Rue on customer info, maintains interest in bid
Following De La Rue's dismissal of rival Oberthur's 895m bid, the world's third largest banknote printer has said De La Rue must reveal the state of relations between it and a key customer, suggesting the work could have been lost.
