Two members of Donald Trump's inner circle are reportedly registered to vote in two states, despite the Republican's pledge to stamp out such behaviour.

The president's chief strategist and senior counselor Steve Bannon is registered to vote in Florida and New York, an investigation by The Guardian revealed, with the news coming in as Trump pledged to tackle voter fraud.

And Trump's nominee for Treasury secretary Steven Mnuchin is allegedly registered to vote in both New York and California, CNN reported, while Trump's daughter Tiffany Trump is registered to vote in both New York and Pennslyvania, Heat Street said.

It is not illegal to be registered to vote in more than one state, provided there is not more than one ballot cast, and in the cases of Bannon, Mnuchin and Tiffany Trump, they are not accused of voting more than once, meaning they did not break the law.

However, Trump classified being registered to vote in more than one state as voter fraud, in a tweet he wrote on 24 January.

Prior to news breaking that several people associated with Trump were registered to vote in multiple states, the president wrote: "I will be asking for a major investigation into VOTER FRAUD, including those registered to vote in two states, those who are illegal and...even those registered to vote who are dead (and many for a long time).

"Depending on results, we will strengthen up voting procedures!"

Trump has alleged that millions of undocumented immigrants voted in the 8 November presidential election, despite a lack of any evidence suggesting this is the case.

He suggested the reason he lost the popular vote to Democrat Hillary Clinton was due to voter fraud rather than more people opting to vote for her.

And news that Trump's former campaign strategist in particular is registered to vote in both his New York place of residence and in a home in Miami-Dade, Florida that has reportedly been empty for months, is likely to leave the president red-faced.