Interim revenue was also down on last year, falling 17% to £209.2m, although pre-tax profit rose 57% to £69.4m thanks to an exceptional gain of £53m on the sale of the group's holding in Camelot.

According to its interim statement, banknote printing volumes will be down 20% for the full year due to a number of factors, including "tenders expected but not won".

Meanwhile the company is still in discussions with the principal customer affected by its paper production issues, believed to be its largest client, the Reserve Bank of India.

However, despite De La Rue's best efforts to put its production issues behind it, investors have continued to punish the company for its failure to draw a line under the losses resulting from the falsification of paper specification test certificates at its Overton mill.

Executive chairman Nicholas Brookes said: "Banknote paper volumes for the full year remain uncertain as customer discussions are yet to be concluded. Pending this, the financial impact on the group for the full year and subsequent years remains unclear."

The company's share price dropped more than 13% in early trading, after the group revealed that the financial impact of the production problems is still impossible to assess.

At the time of writing, De La Rue's share price had recovered to 572p, down 8.2% on the day's opening price of 623p and down almost 44% on the year high of 1,021p.

De La Rue said that it was "encouraged" by the "continued healthy receipt of print and paper enquiries and new orders received in recent weeks" and added that its key objective was to resolve the problems arising from the Overton mill.

To this end the company is introducing independent testing of paper, reassuring its customers, concluding its own internal investigation and dialogue with the SFO and making new management appointments.

On the last point the board said it was making good progress in its hunt for a new chief executive officer and hoped to make an announcement soon.