Guinness owner Diageo has forecast a much bigger than previously expected hit from foreign exchange movements this year after weeks of volatility on emerging markets driven by rising US and European interest rates. 

Diageo, the world's largest distributor of spirits with operations across 180 countries, said it expected currency effects to knock £175m off net sales, compared to a previous estimate of £70m. 

The maker of Johnnie Walker Scotch and Smirnoff vodka said that would also wipe £45m off its full-year profits, up from a previous estimate of £10m. 

"In recent weeks, we have experienced some increased emerging market foreign exchange volatility, which has been partially offset by a strengthening of the dollar," chief executive Ivan Menezes said in an update ahead of its 2018 meeting of shareholders. 

"Based on current rates we currently expect exchange to have a negative impact on net sales of £175m and a negative impact on operating profit of £45m for the fiscal year," Menezes added. 

In results in July, the company, which suffers when sterling rises because it reduces the value of its largely foreign sales, assumed average rates of the pound at $1.35, compared to $1.27 a year ago. 

The company also said it continued to expect operating margins growth of 175 basis points in the three years ending June 30, 2019. 

Organic net sales growth in fiscal 2019 will be "broadly" in line with last fiscal year, Diageo said.