Prosecutors have dropped five charges against a South Australian MP accused of child pornography offences.

The MP, who cannot be identified under state law, was facing 12 charges of possessing child pornography and obtaining access to child pornography.

Prosecutors have dropped all five of the major indictable charges.

Through his lawyer, the MP has pleaded not guilty to the remaining seven minor indictable charges of obtaining access to child pornography.

The case will be listed for a pre-trial conference in the Adelaide Magistrates Court next month.

The statutory suppression on the MP's identity will remain until later in the proceedings.