Democratic presidential candidate Joe Biden on Friday denied allegations by Tara Reade, a former Senate staffer, who said he sexually assaulted her in the early 1990s."This never happened," Biden said in his public remarks on the allegation. The comments come at a critical moment for the presumptive Democratic nominee as he tries to relieve mounting pressure after weeks of leaving denials to his campaign."I'm saying unequivocally, it never, never happened," the former vice president said in an interview on MSNBC's Morning Joe programme. Biden said he will ask the National Archives to determine whether there is any record of such a complaint being filed, but he said repeatedly that he does not believe such a record exists.AccusedReade, who worked as a staff assistant in Biden's US Senate office from December 1992 to August 1993, has accused Biden of pinning her against a wall in 1993 and reaching under her shirt and her skirt.At least two other women have corroborated part of Reade's allegations in interviews with US media outlets. "The former staffer has said she filed a complaint back in 1993," Biden said. "But she does not have a record of this alleged complaint. The papers from my Senate years that I donated to the University of Delaware do not contain personnel files."Biden added that "there is only one place a complaint of this kind could be - the National Archives. The National Archives is where the records are kept."Prior to the MSNBC interview, Biden released a statement saying while the allegations are complicated, "two things are not complicated". Dignity and respect"One is that women deserve to be treated with dignity and respect, and when they step forward they should be heard, not silenced. The second is that their stories should be subject to appropriate inquiry and scrutiny," Biden said in the statement. Republicans, worried about President Donald Trump's increasingly precarious political standing, are seizing on the allegation to portray Democrats as hypocrites who only defend women who allege wrongdoing against conservatives. They are digging in despite the fact that it could renew attention on the multiple sexual assault allegations lodged against Trump.Democrats, meanwhile, are in an awkward position of vigorously validating women who come forward with their stories while defending the man who will be their standard-bearer in what many in the party consider the most important election of their lifetimes."The campaign has issued statements, but he hasn't issued any statements in his own voice," said former Democratic National Committee Chairwoman Donna Brazile. "It's not helping, it's just damaging - not only to the person who has come forward, but it's also damaging the candidate."Came forwardReade, 56, was one of eight women who last year came forward to say Biden had hugged, kissed or touched them in ways that made them uncomfortable, though none accused him of sexual assault. She publicly accused him of the assault on a podcast in March.At the time of the women's statements last year about behaviour that made them uncomfortable, Biden, who had yet to launch his presidential bid, released a video promising to be "much more mindful" of people's personal space.Biden has pledged to pick a woman as a running mate, and the allegation has left those thought to be in contention in a tough spot.