Shares in De La Rue tumbled more than 20 per cent after the banknote printing company cast doubts over its future, suspended its dividend and announced plans to accelerate its restructuring amid growing debts.

De La Rue - which lost the contract to print Britain's post-Brexit blue passport to a French company last year - has warned it could breach its its banking covenant with banks if trading conditions keep getting worse and it doesn't make enough money.

'We have concluded there is a material uncertainty that casts significant doubt on the group's ability to continue as a going concern,' it said along its half-year results.

'Material uncertainty': De La Rue has warned it could breach its its banking covenant with banks if trading conditions keep getting worse and it doesn't make enough money.

It comes as De La Rue slumped to a £9.2million loss in the six months to the end of September, compared to profits of £10million a year earlier, due to charges incurred as a result of the restructuring announced in May.

Shares in the FTSE 250 company fell 20 per cent to 139.60p in morning trading. They have already plunged 75 per cent since rumours emerged in March 2018 that the company had lost the British passport contract.

De La Rue blamed lower demand for banknotes and price pressures for the poor performance, and said that an exodus of senior figures in recent months, including its chief executive, had led to inconsistency in the delivery of its turnaround plan.

'The business has experienced an unprecedented period of change with the Chairman, CEO, senior independent director and most of the executive team leaving or resigning in the period,' said boss Clive Vacher, who replaced Martin Sutherland in May.

'This has led to inconsistency in both quality and speed of execution. The new Board is working to stabilise the management team, which we believe will take some time.'

'At the same time, we have seen significant changes since the start of the year in the market for currency, including pricing pressure as a result of reduced overspill demand.'

But analyst Neil Wilson has a different opinion. He said: 'I don't buy the argument that printing banknotes in a cashless world makes them structurally irrelevant – cash in circulation is growing all the time.

'The need for more secure notes that De La Rue makes is becoming more important, not less. Bad management and decisions seems to be the main reason for the malaise.'

De La Rue saw net debt baloon to £170million, equivalent roughly to its market cap before today's announcement, up from £107.5million a year ago.

However, the company said it expected a better second-half performance thanks to cost savings and improved trading in its currency arm.

It expects underlying operating profits of between £20million and £25million for the full-year.

Shares in De La Rue have plunged 75 per cent since rumours emerged in March 2018 that the company had lost the British passport contract to a French company

De La Rue, which has restructured its operations into two divisions – authenticating goods as genuine and currency services - said its authenticating arm was continuing to see 'good growth' with revenues rising to £33million, from £19.4million a year ago.

De La Rue's product authentication unit creates tracking software and physical labels to help prevent trade in fraudulent items, from cigarettes to official football shirts.

However, there has been speculation that the business could be bought out.

Russ Mould at AJ Bell said: 'The banknote print and security features markets are highly competitive and De La Rue hasn't had the best track record with contract wins of late. We might have simply reached the point where De La Rue is best positioned as part of a bigger company rather than as a standalone entity.

'But would a potential suitor act now or sit on the side lines in hope that the price could get a lot cheaper? After all, De La Rue still has many negative factors to stomach including a fraud investigation into suspected corruption in South Sudan.'