Chip prices could rise after Christmas as supplies of top quality frying potatoes become scarce, according to the British Potato Council.

The long, hot summer and low rainfall stressed out the plants, cutting yields and increasing disease problems such as scab.

The BPC's first estimate for supplies of British potatoes from this year's total crop is 5.53 million tonnes. "It's one of the lowest production years we've ever had and the lowest for ten years," said BPC market analyst Rob Burrow.

That represents a 5% drop on last year, even though the area planted with potatoes was 1% higher than last year. Lower yields in England are to blame - they fell 12% - while Scotland's yields rose by 17%. The majority of production is in England, however.

On top of that there's the quality issue. Scab means much more of the potato is lost in peelings, also pushing up processor costs. "It's not just the volume - we'll have to work harder to use what we've got," said Phil Graham, associate director of agriculture at McCain. "We will have enough potatoes to cover our needs, but raw material prices will increase markedly after Christmas. We're only five months into the season, so there's a long way to go. There could be a sting in the tail - we just don't know!"

Apart from rising chip prices, retailers are unlikely to be seriously affected because they agree contracts for fresh potatoes before the crop is in the ground.

But their need to top up supplies from the open market could see them feeling the pinch as well.

There will be little relief from imports, because Continental countries have suffered even lower yields.

But there is an opportunity for southern Mediterranean countries such as Israel and Egypt to ship more new crop in earlier in the season.