Struggling households came under increased pressure last month as a fall in the number of supermarket promotions triggered an unexpected rise in the rate of inflation.

The Consumer Price Index (CPI) rate of inflation rose to 3.5% in March, from 3.4% in February, the Office for National Statistics said, halting five months of declines and defying City expectations that it would hold steady.

Food and non-alcoholic drinks fell 0.5% on the month but this compared with a 1.4% fall last year, while petrol and diesel prices hit record highs.

Economists said the rise was likely to be temporary but would concern Bank of England governor Sir Mervyn King and the Monetary Policy Committee, who predicted CPI would fall to 2% by the end of this year.