Zed Seselja.

Zed Seselja. Photo: Katherine Griffiths

The Canberra Liberals have come under further financial scrutiny with the discovery that a $20,000 bill for Zed Seselja's 2012 ACT election campaign was charged to both the ACT Legislative Assembly and former senator Gary Humphries.

The bill is for two mass mail-outs of the party's ACT election campaign material, including a letter requesting donations for the Canberra Liberals and another in which Mr Seselja talks about his life growing up in Tuggeranong.

The Australia Post charges went unclaimed and unpaid by the ACT Liberal Party for more than a year.

Legislative Assembly officials and Mr Humphries' former office made repeated requests of the party's management committee and Mr Seselja for the party to pay the bill.

Documents obtained by Fairfax Media through freedom of information laws show staff in the former ACT opposition leader's office notified the Legislative Assembly that it was a party bill when the transaction appeared on Mr Seselja's MLA office account late last year.

The party says the bill was charged to the taxpayer-funded accounts in error.

Mr Seselja said the charges to his former MLA account were added without his knowledge and "I understand that this charge was always regarded as the responsibility of the Liberal Party of Australia ACT and was handled as such".

But the bill failed to reach the Canberra Liberals' ACT division headquarters until last month, despite repeated requests by Australia Post and the Legislative Assembly for the Liberals' correct account details.

Instead it was charged twice more to taxpayer-funded accounts, including to Mr Humphries, who later lost his seat to Mr Seselja in a bitter preselection battle. It is unclear how the charges came to be lodged with the former senator last October and then, again, with the Legislative Assembly in July this year.

The clerk of the Legislative Assembly sent written warnings in October to Mr Seselja, in his new capacity as a senator in the Abbott government, stating that the "unresolved matter" had "the potential to cause embarrassment to both you and the Assembly".

"It is increasingly clear to me that the extensive and repeated efforts made by Assembly officials to resolve this matter are having no effect," the clerk, Tom Duncan, wrote.

Separate correspondence from Mr Humphries' office, obtained by Fairfax Media, shows his staff wrote to the division in March this year to ''stress the urgency of this matter'' and state that the contested charge had been reported to the Department of Finance and Deregulation.

In an email to the former senator's office, party secretary David Connolly wrote that ''it is inexplicable to me why these accounts were sent by Australia Post to you in the first place''.

But the bill remained with Mr Humphries until July, when it was returned to the Legislative Assembly.

Emails, seen by Fairfax, from April, May, September and November this year show repeated requests by Australia Post to the party for its correct account details.

The party supplied account details to Australia Post last month and after Fairfax Media began making inquiries. Correspondence from Senator Seselja's office to Assembly officials says his staffers were liaising with the party to have the charges removed from his MLA account so that it could be closed.

''In June 2013 prior to my resignation from the ACT Legislative Assembly I requested that all accounts held in my name, including an Australia Post account, be closed,'' Senator Seselja said on Tuesday.

''In July, a charge was incorrectly added to this account without my knowledge.

''I understand that the charge has now been appropriately removed and paid.''

The bill is the latest embarrassment for the Canberra Liberals, who were fined $16,500 on Monday for breaching the ACT's electoral laws by not disclosing $38,500 in gifts and donations within the required time.

The party also failed to declare more than $400,000 in debt to the authorities, as required under ACT law.

It reported a $296,000 bank overdraft to the electoral commission last month after the allegations were published.

The party has an additional $140,000 debt to Australia Post that it is disputing.

The $20,000 Australia Post debt for the election mailouts was also not disclosed.

Elections ACT will investigate the debts as part of its routine audit of the territory's political parties, which began at the end of last month.

Canberra Liberals parliamentary leader Jeremy Hanson has repeatedly refused to comment on the matters.

Former party president Tio Faulkner is now working as a staffer in Mr Hanson's office.

The party's new president, Peter Collins, is the division's former finance director.

Liberals Speaker Vicki Dunne told an Assembly hearing on Tuesday: ''I am confident from the briefing I have received that no one sought to obtain a benefit to which they weren't entitled.''