Labor will continue to pursue Angus Taylor over what Tony Burke has labelled his “far-fetched” explanations over how he came to rely on incorrect figures to accuse the Sydney lord mayor and council of spending $15m on domestic travel.

Taylor maintains the erroneous figures came from an annual report document downloaded from the council’s website, despite metadata showing the 2017-18 annual report was loaded in November 2018 and not altered.

After first accusing Clover Moore of peddling a conspiracy theory after Guardian Australia reported the matter, Taylor later apologised “unreservedly” to her for using the incorrect figures.

But he has offered no further explanation over how they came to be included in his letter to her council, first published by the Daily Telegraph earlier this year, pointing to differences in documents’ formats, the result of downloading on different internet browsers, as an illustration more than one document existed.

“Clearly given the document and its various drafts and versions are on the servers of the city of Sydney, only they can prove which documents have existed, and may still currently exist,” Taylor said earlier this month.

He issued the letter to Moore in response to her council calling the federal government to task for its attitude on climate change policy by declaring a climate emergency.

Earlier this month, a Senate estimates spillover hearing heard the department provided information to Taylor’s office about ways to lower carbon emissions in a draft letter to be sent to Moore’s office, but did not include the incorrect figures.

As recently as last week Taylor deflected questioning, telling the ABC he had provided a statement and had nothing further to add.

Spot the difference. The letter the Environment Department drafted for Angus Taylor to send to Clover Moore on the left, and the letter he sent on the right. pic.twitter.com/yOrDtZL7kv — Katie Burgess (@katie_b_burgess) November 12, 2019

But with parliament due to begin its final two-week sitting for the year, Labor said it would not let the matter drop, and Burke has written to Taylor to demand further answers.

“I am aware that you wrote to the lord mayor of the city of Sydney on 31 October 2019 apologising unreservedly for using incorrect figures in a letter you previously sent to the lord mayor,” Burke wrote in the letter seen by Guardian Australia.

“Despite that apology, you have failed to withdraw your claim that the incorrect figures you used in your letter were taken from the city of Sydney’s annual report 2017-18 downloaded from the city of Sydney website.

“… Despite these claims, there is no publicly available evidence that a document containing the doctored travel figures you used in your letter to the lord mayor ever existed on the website. Instead, all the public evidence to date is that no such document ever existed on the website, the altered document has only ever been provided by your office and the doctored figures have only ever been used by you in your letter.”

The last parliament sitting ended with Taylor continuing to insist the information came from the city’s website. After hearing Taylor’s explanations, Labor wrote to the NSW police to ask if it warranted further investigation.

In his latest letter, Burke made a point of reminding Taylor of risks involved with deliberately misleading parliament, which “can constitute a contempt of the House”.

“You have stated in parliament that the information in the letter bearing your signature, sent to the lord mayor of Sydney, was directly drawn from the city of Sydney website. This simply doesn’t add up. You have plainly failed to substantiate the claim you have made in the parliament,” he wrote.

“Deliberately misleading the parliament is both a contempt of the parliament and a breach of the ministerial standards. Your obligation to deal with questions relating to this matter at the first available opportunity is obvious and you are required to honour that obligation as an elected member of parliament and as a minister.”