Federated Farmers says British farmers are acting too hastily in calling for a review of New Zealand's quota of lamb for Europe.
The British livestock board says New Zealand's move from sending frozen lamb to chilled lamb, and from carcasses to bone-in cuts, represents a substantial change to the original deal signed in the 1980s.
The board is poised to ask the European Commission to review the hugely valuable EU lamb quota of 230,000 tonnes.
The chair of Federated Farmers meat and fibre section, Rick Powdrell, said his British counterparts might be basing their comments on just one season's figures.
Mr Powdrell said if the review took place, New Zealand needed to stand up for itself and make a strong case for current arrangements to continue.
British farm leaders say modern technology means much of the quota can be sent as chilled lamb, which competes head-to-head with local fresh lamb.
The North Wales Daily Post reports that, when the original GATT deal was agreed in the 1980s, New Zealand mostly sent low-value frozen carcasses.
The British livestock boards said New Zealand's move from frozen to fresh lamb, and from carcasses to bone-in cuts, represented a substantive change in the trade since the original agreement.
Meanwhile, New Zealand lamb has been caught up in a dispute between Scotland's farmers union and the UK's largest retailer.
Scottish rural leaders are accusing British supermarket chain Tesco of giving their farmers "a slap in the face" by selling New Zealand lamb under a banner proclaiming support for Scottish farmers.
The National Farmers' Union said its Scots arm discovered shelves full of New Zealand lamb in one of the chain's stores, sitting under a banner which claimed it was "The Best Scottish Lamb in Season".
The Farmers Guardian reports local ire is being boosted by the fact the discovery comes at the height of the season for local fresh lamb.
Scotland's farmers union said hard-working local sheep farmers are angry about the situation.
The union said it comes at a time when farmers are facing a difficult year for lamb prices and they are calling on the supermarket chain to address the matter urgently.
Weaker demand, favourable dollar
In New Zealand, a new report has shown weaker demand for some sheep meat is behind falling lamb and mutton prices.
It found weaker overseas demand, particularly for shoulder cuts in China, had softened farmgate prices.
However, the lower New Zealand dollar is expected to lift pre-tax profits almost 10 percent across the sheep and beef sector this season.
It will still be just over 3 percent below the sector's five-year average.