Labour MP John Mann has accused leadership candidate Jeremy Corbyn of ignoring allegations about paedophiles in Islington, north London.
In an open letter to Corbyn, Mann said it was "inappropriate" for him to become Labour leader while a major inquiry into child abuse was taking place. But Corbyn's team hit back, saying it was a "new low in the leadership election".
Dozens of vulnerable children are believed to have been sexually abused in care homes run by Islington council during the 1970s and 1980s. The council has paid hundreds of thousands of pounds in compensation to victims following a raft of independent inquiries. Corbyn has been MP for Islington North since 1983.
In his letter, Mann said a social worker had told him she had met with Corbyn in the early 1990s to raise concerns about child abuse.
Mann told Corbyn: "You said that you would raise the matter with Virginia Bottomley, then at the Department of Health, but no indication of whether you followed this up was ever given."
He added: "The reason that your response and inactions to these matters is worthy of specific scrutiny is that unlike others who did not see what was happening, or as we saw with Savile, kept their suspicions to themselves rather than speak out or investigate, you are wishing to lead the Labour party during the period of Goddard inquiry into child abuse and are seeking become prime minister.
"The so-called 'trendy left' politics of the early 1980s was a contributory factor in covering up child abuse. I myself saw that repeatedly at first hand in Lambeth. Meanwhile children were murdered and disappeared, were raped and beaten, forced into prostitution, trafficked around and a significant number of lives destroyed and blighted.
"Your inaction in the 1980s and 1990s says a lot, not about your personal character, which I admire, but about your politics which I do not."
But a spokesperson for Corbyn said: "This is a new low in the leadership election.
"Jeremy Corbyn has a long record of standing up for his constituents. He called for an independent inquiry into child abuse in Islington at the time and has taken this strong line ever since.
"He has called for the terms of reference of any inquiry to cross local authority and international jurisdiction to ensure as thorough and wide ranging investigation as possible.
"He has commended the home secretary's intention to publish interim reports throughout the process. He has also proposed additional steps such as a standing commission. He has supported Islington Council working closely with the Home Office on these issues."