A fall in lamb numbers because of the worst drought in 70 years may result in higher prices for this year's Christmas roast.

A total of 25.5 million lambs were tailed this spring - 1.3 million fewer than in 2012 - making the current lamb crop the second-smallest in nearly 60 years, Beef and Lamb New Zealand said.

However, the lamb crop figure was higher than many had expected, said Beef and Lamb economic service chief economist Andrew Burtt.

The spring 2013 lamb crop was estimated to be down 7.7 per cent, or 2.1 million lambs, reflecting the severity of the widespread drought last summer and autumn.


Spring lambing conditions would also contribute significantly to the final outcome.

Lamb export prices were expected to average $98 for an 18.4kg lamb this season, up 16 per cent on the provisional 2012-13 price of $84.60.

Federated Farmers president Bruce Wills said the law of economics would kick in and the cost of lamb would rise this year.

"There's no question, if you're a consumer, you're going to be paying more for lamb this year than last," he said.

However, a manager at Westmere Butchery in Auckland, who declined to be named, said he did not expect a large increase in prices between now and Christmas.

"It might be 5c, if that. It won't ever just shoot up."