LONDON - Britain’s child sex abuse inquiry suffered a set back on Thursday with the resignation of its chair Lowell Goddard, who said its "legacy of failure" had weighed upon her role.

Goddard became the third chair to quit since the inquiry was set up in 2014 to examine accusations of historic institutional paedophilia.

"Compounding the many difficulties was its legacy of failure which has been very hard to shake off and, with hindsight, it would have been better to have started completely afresh," said the New Zealander judge in a statement.

"While it has been a struggle in many respects, I am confident there have been achievements and some very real gains for victims and survivors of institutional child sexual abuse in getting their voices heard," she added.

The inquiry has so far launched 13 investigations into claims against politicians and within public institutions.

It was established in the wake of press revelations, confirmed by ministers, that files relating to 114 claims of sexual abuse against children between 1979 and 1999 had disappeared.

Interior minister Amber Rudd said the probe would "continue without delay" and praised the dedication of Goddard, who had previously conducted an inquiry into the police handling of child abuse in New Zealand.

The government has not yet given detail of who will replace Goddard.

"It is a testament to your commitment that you have taken the difficult decision to stand down now, having set the inquiry firmly on course, and allow someone else to lead it through to the end. With regret, I agree that this the right decision," said Rudd.

Goddard had recently faced criticism for spending more than 70 days abroad or on holiday since taking up the position in April 2015.

The decision by Goddard to resign was described as "astonishing" by Keith Vaz, an opposition Labour MP and chair of the Commons Home Affairs committee.

"We will expect a full explanation from both the prime minister and the new home secretary (interior minister) about these matters. We need to examine again the remit, cost, purpose and ambition of what the inquiry was tasked with."

Richard Scorer, a lawyer at Slater and Gordon representing more than 50 abuse survivors at the inquiry, said it is crucial that Rudd appoint a new chair as soon as possible.

"It is incredibly important for survivors that the inquiry continues so the truth is uncovered and their voices are finally heard," he said.

Goddard replaced lawyer Fiona Woolf, who resigned in October 2014 following complaints from victims’ groups related to her establishment ties.

The first chair of the inquiry, Elizabeth Butler-Sloss, stood down just a week into the job after questions were raised about how her brother handled abuse allegations in the 1980s while attorney general. – AFP