Washington DC - President Donald Trump has reportedly instructed the Department of Justice (DOJ) to investigate whether former President Joe Biden's last-minute pardons were delegitimized by his use of an autopen.

In an email obtained by Reuters, the DOJ's pardon attorney Ed Martin said that an investigation is ongoing as to whether Biden "was competent and whether others were taking advantage of him through use of Autopen or other means."

The pardons that would be affected if Biden's signature were deemed void include those directed at members of his family and 37 people on death row.

It is currently unknown whether Biden used an autopen for the signing of his last-minute pardons, but it has been denied by top Democrats.

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Since coming into office in January, Trump has taken aim at Biden's use of an autopen, claiming that signatures generated by such devices are not legally binding, despite having been used since Thomas Jefferson was president.

Claims that the use of an autopen is illegitimate were discredited as far back as 2005, when a DOJ memo confirmed that the president doesn't have to personally sign a bill for it to become law.

In May, Martin himself said that he doesn't believe the use of an autopen is a big issue, telling reporters that, "If you use the autopen for pardon power, I don't think that that's necessarily a problem."

Trump has admitted to regularly using an autopen himself, but caveated the confession by claiming that he never uses it to sign official documents and legislation.

In January, Trump himself pardoned nearly 1,600 people who faced criminal charges for their involvement in the January 6, 2021, attack on the US Capitol.