Joel Andrew Lemmon, 26, was one of two men police charged in October after raids on properties in Amaroo and Kaleen as part of a long-running investigation into an illegal drug syndicate operating in the capital.

ACT Policing said in a statement at the time officers seized drugs with a potential street value up to $700,000, three cars, six firearms, ammunition, a banned weapon and $5500 as proceeds of crime as part of a wider investigation spanning 10 months.

Lemmon and his co-accused, Robert James Masling, 27, were charged in the ACT Magistrates Court with drug trafficking offences stemming from a series of alleged drug transactions of ice, MDMA and cocaine between August and October.

Masling has yet to enter pleas. Both men have been behind bars since their arrest.

The court previously heard Lemmon, of Amaroo, began trafficking drugs earlier this year to remedy money problems and told police he now owed $100,000 to drug dealers with no money to pay his debts.

He had worked for the Finance Department for four years and had top-secret security clearance, the court was told.

Lemmon was back in court on Wednesday, represented by lawyer Adrian McKenna, when he pleaded guilty to five charges of drug trafficking and one charge of drug supply.

His matter was committed to the ACT Supreme Court for sentence.

Masling also appeared in court on Wednesday, when his lawyer, Jacob Robertson, asked for an adjournment.

The men remain in custody. Both cases return to court in December.