Former Plaid Cymru AM Simon Thomas has pleaded guilty to three counts of making indecent images of children.
He admitted all charges put before him at Aberystwyth Magistrates Court.
The court heard Thomas admitted making more than 500 indecent photographs of children and more than 70 films.
He was bailed on condition that he surrendered his passport with police and will have no unsupervised contact with children under 16.
He will appear before Mold Magistrates court on 31 October while pre-sentence reports are being prepared.
Thomas quit the Senedd and his party after being arrested in July.
Helen Mary Jones, who was next on Plaid’s regional list for the Mid and West Wales seat, returned to the assembly to replace Mr Thomas in August.
An NSPCC Cymru spokesperson said: “Thomas has admitted very serious offences and by accumulating this vile material has helped fuel the demand for more to be created and for more harm to be inflicted on vulnerable, young people.”
Source BBC News