Donald Trump. Getty Images President Donald Trump on Tuesday called for a "major investigation" into his baseless claims of widespread voter fraud — but his own lawyers are on record saying there is no such evidence that such fraud exists in the US.

Late last year, attorneys representing Trump wrote as much in court filings submitted to squash recount efforts by Green Party presidential nominee Jill Stein in Michigan and Pennsylvania, The Washington Post reported in December.

In the filing submitted in Michigan on behalf of Trump's campaign, Trump's lawyers made a direct statement that no evidence pointed to voter fraud existing in the 2016 election.

"On what basis does Stein seek to disenfranchise Michigan citizens?" the filing said. "None really, save for speculation. All available evidence suggests that the 2016 general election was not tainted by fraud or mistake."

The lawyers wrote that the purpose of Stein's recount effort was "to sow doubts regarding the legitimacy of the presidential election."

The filing in Pennsylvania did not go quite as far, limiting its analysis only to the state.

"On what basis does Stein seek to disenfranchise the voters of the Keystone state?" it said. "None really. There is no evidence — or even any allegation — that any tampering with Pennsylvania's voting systems actually occurred."

Trump secured the presidency in the November 8 election with 306 electoral votes to Democratic nominee Hillary Clinton's 232. Clinton, however, won the popular vote by nearly 3 million.

In late November, Trump first made the baseless claim that "millions" had voted illegally in the election and had swung the popular vote in Clinton's favor. He also claimed without evidence that "serious voter fraud" occurred in Virginia, New Hampshire, and California — all states that he lost. The secretaries of state for each of those three states strongly rebuked Trump's assertion and said no such fraud took place.

Trump's false assertions were brought back to the forefront this week when he made a similar claim during a meeting on Monday evening with congressional leaders, much to the dismay of several Republicans. Trump's claims that voter fraud had an impact on the election have repeatedly been shot down by fact-checkers and voting officials.

Reporters grilled the White House press secretary, Sean Spicer, about Trump's claims on Tuesday, with Spicer saying the voter-fraud claim was "a longstanding belief he's maintained." He added that the "belief" was based on "studies and evidence" Trump had been presented. Spicer said the president believed that as many as 3 million to 5 million people voted illegally in November's election.

The study cited by Spicer, and one previously cited by Trump during the campaign, did not prove Trump's assertions. Authors of both studies have said they did not prove Trump's assertions.

When asked whether this belief would spark an investigation, Spicer said "maybe we will." He did not answer whether he personally believed that millions voted illegally.

Trump followed up on Wednesday morning by announcing his intention to start an investigation.

"I will be asking for a major investigation into VOTER FRAUD, including those registered to vote in two states, those who are illegal and," he said in an initial tweet, adding, "even, those registered to vote who are dead (and many for a long time). Depending on results, we will strengthen up voting procedures!"