New Zealand Food Safety has issued a health warning for shellfish on Christchurch beaches

People are advised to avoid collecting or consuming shellfish due to the presence of diarrhetc shellfish toxins.

Deputy director general Vincent Arbuckle says routine tests on greenshell mussels from Sumner have shown levels over the safe limit.

He says it includes a range of shellfish such as oysters, scallops and kina.

The warning extends from Waimairi Beach to Adderley Head in Lyttelton Harbour.