Growers have warned of an onion shortage after the summer heatwave, with this year's harvest likely to be 25pc down for both the quantity and size of the bulbs.

British Onions chairman Tim Elcombe said a lack of large onions could affect the availability of supermarket three-packs.

He said: 'The hot weather we have experienced in June and July have put the onion crop under considerable stress affecting both yield and bulb size.

'Growers and their staff have been working round the clock to keep crops irrigated, however there are a number of areas of the country where water abstraction is being limited and their own reserves are very low. Crops are irrigated at this time of year to put on weight and size. Irrigation is currently just keeping the plant alive – crops without irrigation are dying.

'Although there is still some way to grow for most crops, the reduced yield potential for most is already apparent. Most crops are going to suffer from a lack of large onions, which will have an impact on availability of the three-in-line pack formats which are sold in most retailers.'

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