Retesting Failed Laboratory Samples


The law enforced by Port Health sometimes requires a sample to be taken and sent for laboratory analysis.  Samples may also be taken for monitoring purposes or in response to intelligence.  If the sample fails and the importer disputes the result there is a process set out in law that needs to be followed.

When samples are taken by Port Health for laboratory analysis, other than microbiological analysis, the sample is normally divided into three parts. This is carried out either by Port Health at the time of sampling or at the Laboratory after preparation of the sample for testing.

Part 1 of the sample is the Port Health sample and will be analysed by the laboratory

Part 2 is for the importer and is referred to as the defence sample and can be made available for testing by the importer’s own laboratory

Part 3 is referred to as the referee sample and is retained for independent analysis should there be a dispute

Importers own Analysis

If the importer wants to arrange to have their defence sample tested then arrangements need to be made to send the sample to a laboratory for testing.

If your sample is being analysed for genetically modified rice or rice products from China you will need to follow the guidance from the Laboratory of the Government Chemist otherwise your result will be deemed to be invalid. The advice can be found here:

Selecting a Laboratory

The laboratory selected cannot be the same laboratory that Port Health used as it would be considered a conflict of interest. The laboratory must be accredited to carry out the required tests to the recognised ISO standard. There is a list of approved official feed and food control laboratories available on the FSA website – other accredited laboratories may also be used.


The Importer is responsible for arranging the collection and submission of their defence sample to their selected laboratory, together with payment of associated costs.   Details of the chosen laboratory and a contact name will be required so that the sample can be dispatched.

Results of the Defence Sample

If the defence sample result agrees with the Port Health findings then this is binding and the Port Health decision to refuse the consignment applies.  If the defence sample result does not match the Port Health result a further, referee analysis can be carried out.

Note:- It is sometimes possible to by-pass this stage and send the referee sample directly to the Laboratory of the Government Chemist (LGC) (see the following section) without the importer’s own analysis being conducted.  This must be carried out with the prior consent of LGC and is usually in exceptional circumstances. If this is carried out then the sample costs from LGC may be significantly increased and SCPHA will not be responsible for 50% of the costs as in the standard procedure, i.e. the Importer will be responsible for all costs.

The Laboratory of the Government Chemist – Resolving Disputes through Referee Analysis

In the UK the Official Arbitrator is the Laboratory of the Government Chemist (LGC). The Government Chemist will carry out further testing on the referee sample and will make a binding decision. The analysis that is carried out is extensive and the process is very detailed so this analysis can be more time consuming than the official control laboratory analysis. Click here to read more about submitting a referee sample to the Government Chemist.

LGC will analyse the referee sample and provide the final result and decision for the consignment.  This decision must be adhered to by all parties.  Port Health will pay 50% of the final analysis cost where there is a dispute between the results of the Port Health sample and the defence sample.

If the Importer wants to use the LGC arbitration service it is the importer’s responsibility to contact LGC and make initial arrangements.  Further details of the procedure are available from the LGC.  Once the dispute has been raised LGC will then contact Port Health to get the sample details.  Port Health will then ask our laboratory to send the referee sample to the LGC.

When is retesting not possible?

In the case of microbiological samples / contaminants, due to the highly perishable nature of the products concerned a sample for referee analysis may not be provided.  There are also issues with the distribution of micro-organisms within a food consignment which may not be homogenous (evenly distributed). For example if salmonella are detected in the test sample but not in the defence sample this does not mean that salmonella were not present and the food is safe to eat.