A typeface is at the heart of a Pakistani scandal after investigators accused Prime Minister Nawaz Sharif's daughter of presenting forged documents to a corruption probe against the Sharif family.

Microsoft's Calibri font was used to type certified papers naming Maryam Nawaz as a trustee of several high-end flats in central London.

But the papers were dated a year before Calibri was in widespread commercial use.

The properties, bought using offshore companies, are at the centre of a case against the Sharif family, with authorities and the opposition questioning the legitimacy of funds used to buy the apartments.

Maryam Nawaz, Sharif's political heir, claimed she did not own the flats.

In a report issued earlier this week, investigators tasked by Pakistan's Supreme Court to look into the allegations said the documents she submitted were "falsified" as they were dated February 2006 and the font in which they were typed in was not released until 2007.

The controversy over the flats erupted last year with the Panama Papers leaks and could unseat Sharif.

READ MORE: Pakistan court resumes Sharif 'corruption' hearings

The joint investigative team (JIT) based its conclusion on an assessment by London's Radley Forensic Document Laboratory.

Dubbed #Fontgate, the revelation set Pakistani social media alight with jokes and memes.

Today #calibri was searched more than porn in Pakistan — Sherry (@CherieDamour_) July 11, 2017

Who cares about Covfefe when the entire government can crumble due to #Calibri! — Ali Akber (@aliakberhabib) July 11, 2017

#Calibri font was introduced in 2007 but the 'Innovative Sharif Family' used it in 2006. Microsoft pe bhi qabza kar lia?😂 #FontGate pic.twitter.com/sXz4RlFgRv — Safi Ullah (@safigraphy) July 11, 2017

The uproar has also added fuel to calls for the prime minister to step down, a demand Sharif on Thursday rejected.

Journalist Mubashir Zaidi said Sharif should now write his resignation "in Calibri font".

PM should now inaugurate 420MW 'Isteefa' dam (damn) #GameOverNawaz #PanamaJIT And that too written in #Calibri font — Mubashir Zaidi (@Xadeejournalist) July 12, 2017

In another twist, Twitter users noted the Wikipedia entry for "Calibri" had been edited repeatedly following the revelations. The online encyclopaedia has since temporarily suspended edits to its page on Calibri.

Typeface designer weighs in

Supporters of Sharif's ruling PML-N party argued that Calibri has been publicly available since 2004.

But the font's creator, a Dutch designer named Lucas De Groot, told the AFP news agency in a statement that it was "unlikely" Calibri had been used in any official documents in 2006.

"[In] my opinion the document in question was produced much later," he said.

De Groot said he began designing Calibri in 2002 and sent the finalised version to Microsoft in 2004. After that, he said, it was used in beta versions that would have required "serious effort" to obtain.

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Maryam Nawaz, herself a regular Twitter user, has not yet commented publicly on the Calibri claim, though she vowed the JIT report itself would be "decimated" in court.

Sharif's PML-N party insists the wealth used to buy the properties was acquired legally, through family businesses in Pakistan and the Gulf.

But the JIT report said there was a "significant disparity" between the Sharifs' income and lifestyle.

The Sharif family has consistently denied the allegations against it and rejected the JIT report.

The Supreme Court is considering its next steps and will begin deciding what action to take next week.