New Zealand’s meat exports are being blocked at the border into China with authorities apparently rejecting them because of a name change on an export certificate.

The stop at the border could mean thousands of tonnes of New Zealand sheepmeat will either be stuck at port or on the water en route to China.

China was the largest buyer of New Zealand’s sheepmeat by both volume and value in the first quarter of the year.

Every meat company exporting to China is believed to have been affected by the block, which first emerged at the end of April.

The block relates to import certification issues caused by the Ministry of Agriculture and Forestry being renamed the Ministry for Primary Industries (MPI) as part of an industry merger.

However, a top meat industry source said this was being used by Chinese authorities as an excuse to protect local pork and poultry industries.

The source noted that the industry merger was completed in April 2012 and that China had continued to allow imports of both dairy products and beef hides throughout the meat block.

Officials at MPI learned of the issue on Monday, informing Primary Industries Minister Nathan Guy on Tuesday, 3News reported tonight.

But the Government kept quiet about the block all week. A spokesman for Guy did not respond to requests for comment.

In a statement, MPI said the name change on export certificates took effect from the start of March, which appeared to be behind the issue.

Staff at the New Zealand embassy in Beijing were working with authorities to try to have the meat cleared, none of which had been destroyed.

Meat Industry Association chief executive Tim Ritchie said there was no issue with quality or food safety, with the problem appearing to be purely related to documentation.

However, the issue could cause long term damage the industry if it continued, Ritchie said.

‘‘If it’s not sorted out very quickly it will be very serious.’’

Meat companies would have to wait longer to be paid, while the product would also be incurring rising costs from having product stuck at port, Ritchie said.

‘‘The other issue is the flow on effect to customers sitting there waiting for product, either for retail or for their own processing.’’

Labour primary industries spokesman Damien O'Connor said the issue followed an ‘‘inadequate’’ response to the DCD scare by the Government.

‘‘National has sat on this issue for almost a month when it should have moved swiftly to rectify the problem, reassure the meat industry and satisfy the Chinese Customs Service.’’