Car manual firm Haynes Publishing swung to an annual loss after being hit by "challenging" trading at its US business.

The Yeovil-based firm, which has sold 150 million manuals since 1960, posted a full-year pre-tax loss of £7.2 million in the year to the end of May, from a £2m profit a year earlier, after booking a £9.7m of impairment charge at its key American unit.

The publisher of guides on everything from motorcycle repairs to preparing for retirement said its US and Australian businesses felt the impact of inventory reductions from four important retailers.

It said its annual sales for its US and Australian business fell 13 per cent to £14.7m in the period.

In the UK and Europe it has invested heavily in digital technology, allowing its vehicle manuals to be transmitted to over 40,000 professional mechanics across the region.

Sales across these territories fell 11 per cent to £11.9m, although the firm added it was starting to see benefits of its IT upgrades flow through as it picked up new customers and extended existing relationships.

Chairman, and son of the founder, JHC Haynes said: "Our final year results are reflective of the challenging trading conditions that we are encountering in all consumer markets."

"The second half of the year was stronger, as expected, but the business continues to be affected by these challenging trading conditions, most notably in our important North American market."

The business reiterated that the wide-ranging cost and operational review of the group announced in September will be presented to the board in early 2016.

The business also said that its chief executive Eric Oakley and chief financial officer Dan Benhardus will leave the firm after 35 and 27 years respectively at the end of the next financial year. It said the board will begin the search for new replacements.

It added that it had hired Andrew Golby as its global digital director who takes up his post next month. He will be tasked with overseeing the roll-out of the firm's new US and Australian website and a range of other digital initiatives.

Founder John Haynes wrote and published his first book, on building an Austin 7 Special, while he was still at school in 1956.

The firm was launched four years later and publishes manuals on health, history, leisure and DIY in 15 languages including Russian and Chinese.