Maent yn cael eu penodi gan y Prif Weinidog i helpu Gweinidogion ar faterion lle mae gwaith y Llywodraeth a gwaith Plaid y Llywodraeth yn gorgyffwrdd a lle y byddai'n amhriodol i weision sifil parhaol gymryd rhan. Maent hefyd yn adnodd ychwanegol ar gyfer Gweinidogion gan ddarparu cymorth o safbwynt sy'n fwy ymroddedig ac ymwybodol yn wleidyddol nag y byddai modd i’r Gwasanaeth Sifil parhaol ei gynnig i Gweinidog.
They are appointed by the First Minister to help Ministers on matters where the work of Government and the work of the Government Party overlap and where it would be inappropriate for permanent civil servants to become involved. They are an additional resource for the Minister providing assistance from a standpoint that is more politically committed and politically aware than would be available to a Minister from the permanent Civil Service.