The attorney general, Christian Porter, has told parliament he did not need to seek advice from his officials or agencies, or give advice to the prime minister, before witnessing a controversial call between Scott Morrison and the New South Wales police commissioner, Mick Fuller, last week.

Porter was forced to shrug off persistent questioning about his judgment as the first law officer of the land on Monday. “It was not the sort of phone call, because it was so basic and simple, that required any advice to be sought or given,” the attorney general said.

With Labor resuming its pursuit of the Angus Taylor imbroglio – this time targeting Porter after it was revealed at the weekend that he was present when Morrison called Fuller to check the substance of a police investigation into the minister for emissions reduction – the attorney general attempted to return fire by arguing previous Labor referrals to the police were vexatious.

Porter sought to minimise the seriousness of the current process under way in NSW, where Strike Force Garrad has been formed to investigate if any criminal offences had been committed in relation to a doctored document that Taylor used to attack the travel expenses of the Sydney lord mayor, Clover Moore – an erroneous political sledge the minister subsequently apologised for.

The attorney general told parliament the opposition had tried on eight occasions to refer various matters to the police with “zero success”, and said there was no need to take advice before listening in on the call between the prime minister and the police commissioner in the middle of an investigation into one of their colleagues. Porter said it was a short conversation and “the descriptions of that call provided by the prime minister and commissioner Fuller have been absolutely accurate”.

Morrison’s call to the commissioner has been criticised as a misjudgment by former prime minister Malcolm Turnbull, and it was described last week by the former anti-corruption commissioner and senior judge David Ipp as obviously inappropriate. But Porter declared the conversation “totally appropriate”.

Porter also referenced Fuller’s public account of the conversation to downplay the gravity of the probe. The police commissioner told journalists, referring to the Taylor matter, that “these types of investigations can consume an enormous amount of resources from NSW police and they are a great diverter of my time”.

As well as the pursuit of Porter, Taylor also faced fresh questions on Monday about his pecuniary interests. The minister was asked why he had failed to declare partnership shares in a company called GFA F1 Pty Ltd for more than five years.

One of Taylor’s companies, Gufee, has an interest in Farm Partnerships Australia, which has been declared – and Farm Partnerships Australia has a shareholding in GFA F1 Pty Limited. The minister shrugged off the question. “My interests are declared in accordance with the rules, as I have said many times in this House,” he said.

The Labor leader, Anthony Albanese, declared that Taylor had now “been embroiled in four scandals this year”. But Morrison launched a stout defence of Taylor’s record in his portfolio. The prime minister said the emissions reduction minister had presided over many achievements, including investments in grid reliability, a strategy to develop hydrogen, and passing the “big stick” legislation.

MPs have returned to Canberra for the final parliamentary sitting week of 2019, and the protracted Taylor controversy is generating speculation within the government about the origins of the dodgy document at the centre of the saga, as well as unease and frustration around the Coalition.

The Senate on Monday also voted to order the Morrison government to produce documents relating to the call to the police commissioner by noon on Tuesday.

Taylor has denied consistently that either he, or anyone in his office, altered a City of Sydney document to inflate travel expenditure. Taylor has said the document with the incorrect numbers was obtained from the council website.

But the council has produced evidence showing that its publicly available annual reports has only ever contained accurate figures. Metadata and screenshots from the council’s content management system showed the annual reports on its website had not been changed since they were uploaded with the accurate figures 11 months ago.

The differing accounts prompted Labor to refer the matter to NSW police, asking for an investigation into whether a forgery had been created to influence the mayor in her public duties.

Fuller signalled last week he wanted the current investigation to be conducted expeditiously. The NSW police commissioner told journalists: “There is a whole range of reasons why I want the matter finished quickly but professionally, and many of those are selfish.”