Defence contractor Chemring Group has issued a profit warning after a delay in revenue from an ammunition supply deal in the Middle East.

It said a cash advance payment of £12m associated with the contract may not be received until its 2016 financial year.

As a result the business lowered its forecast for full-year underlying operating profit by nearly one third.

That saw its shares fall by more than 40 per cent to a 10-year low in early trading.

Chemring, which makes products including ejector seats for fighter jets and flares used to counter heat-seeking missiles, cut its forecast for 2015 underlying operating profit to £33 million, from £49m.

The company, which employs more than 200 at its Energetics UK business in Ardeer, Ayrshire, has been struggling with delays in its Middle Eastern contracts as well as defence budget cuts in key markets.

Figures released in June showed that defence spending by NATO countries is set to fall again this year in real terms.

Chemring chief executive Michael Flowers said the ammunition products are ready but the business is still waiting on the "receipt of necessary permits and export approvals associated with this contract".

Mr Flowers added: "Given the proximity of our year end, the board considers that there is now a realistic prospect that the Group does not receive these permits and approvals in time to recognise revenue under the contract in the current financial year."

Chemring said it would also speak to its creditors about amending the terms of its debt covenants, and plans to raise up to £90m through a rights issue which is likely to take place early next year.

In a note Panmure Gordon analyst Sanjay Jha described the update as a "horrible profit warning" and cut the rating on the Chemring stock from buy to sell.

Chris Dyett from Investec said it will be a "meaningful miss to profit expectations" and added: "The company is likely to be close to its banking and loan note covenants. The company will seek to negotiate amendments and a waiver."

Mr Flowers said managing the company's debt had hampered its ability to focus on operations.

"The recent progress of the group has been impeded by its high levels of debt and associated interest costs," he said.

The company had net debt of £149m as at 30 April.