Donald Trump has filed a lawsuit in Pennsylvania claiming voters were held to "different standards" as he launches his bid to challenge the US election results.

The lawsuit alleges a "two-track system resulted in voters being held to different standards depending on how they chose to exercise their right to vote."

On Saturday the US President doubled down on his unfounded claims about voter fraud, claiming "bad things happened".

He insisted he won the election with "legal votes" in a tweet.

Social media giant Twitter quickly added a disclaimer on to his posts, saying, "This claim about election fraud is disputed".

Donald Trump's team have questioned the results of the US Election

Trump's attack on the integrity of the US Election has focused largely on mail-in ballots, with his camp also saying that observers were prevented from entering various polling stations and were then made to stand a distance away from the ballot counting machines.

And now Trump will challenge the US election results in court after a complaint for declaratory and injunctive relief was filed with the United States District Court for the Middle District of Pennsylvania.

The lawsuit alleges: "In a rush to count mail ballots and ensure Democrat Joe Biden is elected, Pennsylvania has created an illegal two-tiered voting system for the 2020 General Election, devaluing in-person votes.

"For voters that appeared at the polls, those citizens were required to sign voter registrations, have those signatures checked against voter rolls, vote in a polling place monitored by statutorily authorised poll observers, and have their votes counted in a transparent and verifiable open and observed manner.

Donald Trump has refused to admit defeat

"By contrast, due to the arbitrary, unauthorised, and standardless actions of the Secretary of the Commonwealth of Pennsylvania, Kathy Boockvar, nearly 2.65 million votes were cast through a “mailin” process that lacked all of the hallmarks of transparency and verifiability that were present for in-person voters.

"In fact, Secretary Boockvar affirmatively excised nearly every element of transparency and verifiability. Among other things, the Secretary refused to require adequate verification of the voter’s identity.

"Rather than require votes to be received on the day of election, the Secretary permitted ballots received up to three days after the election to be counted without any evidence of timely mailing, such as a postmark.

"Finally, contrary to the in-person voting that is open and transparent to the parties and the candidates, Defendants permitted the review and counting of mail-in ballots largely in secret with no monitoring."

It adds that: “different standards have been employed in different counties across the Commonwealth of Pennsylvania to determine whether an absentee ballot should be counted” is the “kind of disparate treatment” that violates “the equal protection clause because uniform standards will not be used statewide to discern the legality of a vote in a statewide election.”