Prime Minister Scott Morrison is refusing to publish details of two missing advertising and media contracts worth more than $100 million that preceded his sacking as Tourism Australia’s managing director in 2006, insisting they are confidential because the services they covered were delivered overseas.

On Thursday, the senate supported a Labor motion to order the government to produce “all documents” relating to any contracts Tourism Australia entered between January 1, 2004 and January 31, 2006. It demanded the contracts be tabled by 10am on Monday.

The two contracts Morrison had specifically declared confidential are understood to have been signed in Australia. The first one, for global creative advertising services, covered the design, production and rollout of the controversial “Where the bloody hell are you?” tourism campaign, which involved a television advertisement filmed onshore.

The prime minister’s argument, delivered in a letter to the senate by Finance Minister Mathias Cormann, contrasts with information published about the tenders before the contracts were let.

Details of the contracts themselves are not available on the AusTender website, where government contracts are posted. But the original tender details were published and remain on AusTender, listing the location of the two then-prospective contracts as “ACT, NSW, Vic, SA, WA, Qld, Tas, Other, Overseas”.

As political pressure on the prime minister increased this week, after a disastrous Victorian state election result and the defection of Liberal MP Julia Banks to the crossbench, Morrison and Cormann doubled down on their refusal to respond to questions about the prime minister’s ill-fated tenure as head of Tourism Australia in 2005 and 2006.

That period was the subject of a scathing 2008 Australian National Audit Office (ANAO) report that disclosed what preceded then tourism minister Fran Bailey’s decision to sack Morrison, backed by then prime minister John Howard and his department.

The auditor’s review was among 40 ANAO reports across government tabled that year. It was not among the handful that the watchdog joint committee of public accounts and audit earmarked for further scrutiny.

The reasons for Morrison’s dismissal – variously blamed on a personality clash with Bailey and the controversy surrounding the contentious ad campaign featuring model Lara Bingle on a beach – have never been officially confirmed. The Saturday Paper discovered the overlooked audit and published its contents three weeks ago.

The audit focused on three major contracts worth a total of $184 million but singled out the first two for particular criticism, detailing non-adherence to procurement guidelines, poor record-keeping, actioning an unsigned contract and withholding financial information from the board.

While the audit did not mention Morrison by name, the contracts were executed under his stewardship as agency head.

Before publication, neither The Saturday Paper nor AusTender staff could locate the contracts on the AusTender website.

The Saturday Paper also submitted 18 written questions to the prime minister’s office related to both those findings and to Morrison’s tenure at and dismissal from Tourism Australia.

Despite repeated requests over three weeks, there has been no response.

It is unclear if the government will comply with the senate direction to table the missing contracts and associated documents on Monday.

After The Saturday Paper report appeared, the Opposition used a senate-only sitting week to ask questions about the ANAO’s findings.

Representing the prime minister, Senator Cormann initially tabled a letter saying Morrison had fulfilled the terms of his Tourism Australia contract and citing statistics on the success of the “Where the bloody hell are you?” campaign.

This week, answering a previous question from the Opposition about the missing contracts, Cormann tabled another letter, quoting 2005 Commonwealth procurement guidelines and a separate 2005 guidance on publishing obligations that said details of any contract delivered overseas should not be published.

The senator said this was why the contract summaries were not available on the AusTender website.

The details of a third contract, which the auditor-general also examined in the Tourism Australia report but about which it had less concern, are listed there.

The subsequent contracts for global creative services and media services are also on AusTender, signed in 2008 with new contractors upon the expiry of the original now-missing three-year versions.

The 2005 global creative advertising contract that resulted in the “Where the bloody hell are you?” campaign – credited with adding $2 billion to the Australian economy – was awarded to M&C Saatchi.

Morrison had engaged the same company when he was head of New Zealand’s Office of Tourism and Sport in 1998. It was responsible for the highly successful “100% Pure New Zealand” campaign.

In his letter tabled this week, Cormann said the 2005 publishing guidance “explicitly required that contracts for goods and services procured overseas and used overseas ‘must NOT be reported on AusTender’ ”.

“The Australian National Audit Office Report of 2008 itself states: ‘most of Tourism Australia’s procurement activities are exempt under the CPGs (Commonwealth Procurement Guidelines) because they involve the procurement of property or services outside Australia for consumption outside Australia, or the procurement of Government advertising services,” Cormann wrote.

The senator chose not to include the next sentence of the audit report, which reads: “Nevertheless, where Tourism Australia chooses to procure services using a method covered by the CPGs, it is expected to follow the CPGs’ requirements.”

Cormann’s letter said: “Tourism Australia has advised my Department that these contracts were for services that were provided overseas. As such, I can advise that the contracts complied with the reporting obligations in place at the time.”

The Saturday Paper asked Tourism Australia about the missing contracts more than two weeks ago and was told repeatedly that officers were looking into the issue.

This week, after Cormann’s letter was tabled, Tourism Australia was asked again. The organisation’s spokeswoman replied that Cormann’s letter was its response.

Asked if it was Tourism Australia’s position that no part of either contract was executed in Australia, the spokeswoman replied: “We are unable to provide further details and the relevant personnel are no longer with the organisation to clarify further particulars.”

She did not acknowledge that Tourism Australia’s former managing director is now the prime minister.

The responses came during a difficult week for Morrison. On Tuesday, just as he was attempting to seize back the agenda by announcing that next year’s federal budget would be brought forward a month to April 2 and would include an earlier-than-forecast surplus – boxing in the election date as either May 11 or 18 – Victorian backbencher Julia Banks stole his limelight by quitting the Liberal Party to become an independent.

Banks had only alerted a few close colleagues of her intentions – including new independent member for Wentworth Kerryn Phelps – but not Morrison.

“The gift of time and reflection has provided some clarity regarding the brutal blow against the leadership,” Banks said, describing Malcolm Turnbull and his former deputy Julie Bishop as “visionary, inspiring leaders of sensible centrist liberal values”.

She blamed “members of the reactionary right wing” who she said acted for themselves.

“The aftermath of those dark days in August then acutely laid bare the major parties’ obstructionist and combative actions and internal games – all for political point-scoring rather than for timely, practical, sensible decisions on matters which Australians care about,” she said, referencing Turnbull’s removal from the prime ministership.

Banks called for equal representation of men and women in parliament to create “a culture change”.

Conservatives labelled her a rat and, privately, worse.

Although she guaranteed not to back a no-confidence motion in Morrison or the government nor block supply, Banks’s departure further reduced the Coalition’s grip on power, leaving it with just 73 members out of 150 in the house of representatives. That means it needs support from Labor, the Greens or the crossbench to pass any legislation and faces the risk of having changes forced upon it that it does not want.

Banks’s move – which some colleagues condemned and others cheered quietly – gives the crossbench greater power to pressure the government on a range of issues, including moving refugees and asylum seekers out of offshore detention and introducing a national integrity commission.

Phelps and fellow crossbenchers announced on Thursday that next week they would push to have the last detainee children removed from Nauru.

They are also considering whether to refer Home Affairs Minister Peter Dutton to the High Court to determine if he is constitutionally eligible to remain in parliament, due to his family’s childcare businesses having received government subsidy.

Dutton missed parliament this week after breaking his arm and requiring surgery at the weekend. As is standard for medical leave, the Opposition provided a pair – meaning one of its MPs abstained from votes – so the government was not disadvantaged by his absence.

The manager of government business, Defence Minister Christopher Pyne, has warned that if non-government MPs move to refer Dutton, then other MPs, including several on the Labor side who have faced questions about their own eligibility, might also be referred.

The Victorian election result emboldened some Liberal moderates and others in the party to also speak out, issuing public demands to eschew a conservative social agenda they say is working against them.

Julie Bishop called on her party to do a deal with the Opposition to introduce the national energy guarantee, the policy that cost Turnbull his job and which Labor has now adopted.

As parliament rose, Morrison headed off on a lightning-fast trip to Argentina for the Group of 20, accompanied by Cormann in place of Treasurer Josh Frydenberg.

Banks’s defection made the numbers too precarious to risk having two lower house ministers away, so Frydenberg stayed behind.

He will be keeping an eye on things while Morrison delivers services overseas – just like those two contracts he arranged that nobody is allowed to see.