A Norfolk farm has been forced to sell off tonnes of premium vegetables as animal feed – because a quirk of climate has led to them growing too large to sell to retailers.

Giant parsnips have become a problem at Tattersett Farms, near Fakenham, which produces root vegetables for a supermarket and has to meet strict size and quality control specifications as part of its contract.

The warm spring, combined with intensive irrigation during dry periods, created ideal conditions early in the year.

But then the above-average warmth of the autumn, coupled with a lack of demand, extended the growing season and led to the huge specimens now being harvested.

The farm's pre-packaged parsnips can be no larger than 45mm in diameter, while 45-75mm can be sold loose. But this year, many parsnips were more than 100mm in diameter, meaning 10pc of their crop was too big to sell.

To avoid wasting the crop, the surplus is being sold at a fraction of its wholesale value to livestock farmers as animal feed.

Oliver Hammond, the farm's technical manager, said: 'We are virtually giving it away.

'The parsnips had an ideal six or seven months. We irrigated them and they kept growing and growing, but with it being so warm lately there has been no frosts to knock them back. Plus there has been no demand.

'People were still having barbecues in October, not roast dinners, so we couldn't get them out of the ground early because we would have no-one to sell them to.

'It is nothing to do with the supermarkets, it is just the climate. If we knew the weather was going to carry on this warm for so long we wouldn't have irrigated so much – but there was no way of knowing that.'

Mr Hammond said it was difficult to suddenly find markets for over-sized produce.

He said: 'There are people who are already growing stuff larger for processing in soup or baby food factories, so you cannot turn up with 50 tonnes and get an elbow into those markets, as they already have their suppliers and their quotas.'

Brian Finnerty, a National Farmers' Union spokesman for East Anglia, said he was not aware of a widespread regional problem with oversized vegetables.

'Growers have worked very hard to deal with the vagaries of the British weather,' he said. 'But if there is a crop which has not made their specifications for any particular reason we have got a lot of contacts in wholesale markets, and we would encourage them to find other ways to sell their produce.'

George Rivers, of the British Carrot Growers' Associaton, said: 'The dry conditions have had quite an impact.

'When we are talking about root vegetables, the dry conditions in March and April meant the carrots would tap downwards looking for moisture and they tend to be long, but not thick. That could become an issue for pre-packaged produce.

'The profile of the crop is not ideal, but it should not lead to a high level of wastage. The larger producers are looking at processing facilities on site which could turn waste product into a revenue stream.'

Sarah Cordey, spokesman for the British Retail Consortium which represents supermarkets, said: 'Retailers work hard to keep food waste to minimum. Where produce is mis-shapen or, in this case, the wrong size, they are keen to promote it in budget ranges or make use of it as ingredients in ready meals. There are lots of potential destinations for fruit and veg of all shapes and sizes.'