SYDNEY. The ABC's head of investigations and current affairs has walked out after 25 years at the national broadcaster, in the latest fallout from the Four Corners source scandal that has engulfed the network.

Jo Puccini's resignation was confirmed to staff by email, with the ABC acknowledging her contribution to flagship programs including Four Corners, Media Watch, Lateline, 7.30 and the national reporting and investigations teams.

Her departure comes as the broadcaster grapples with the fallout from the sacking of Four Corners reporter Mahmood Fazal and the withdrawal of three of his programs over concerns about the veracity of sources.

“It's been an adventure and a privilege to work at the national broadcaster, an institution where I've made lifelong friends,” Ms Puccini said. “It's now time for a new chapter in my career.”

She said she was proud of the journalism she had helped produce and the impact it had on helping the ABC's audience understand the issues and events that affect them.

The resignation follows a bruising period for the ABC's prestige current affairs stable. Three episodes produced by Mr Fazal — Cocaine Highway, Meth Highway, and Remy was 12 when she became a drug dealer — have been pulled from air.

An ABC spokesman said the action had been “taken following concerns identified about the veracity of sources used in the three programs”.

Allegations emerged that a source being interviewed in the Four Corners episodes was the same person, but had been given different names while their face was obscured by a mask.

The former Mongols bikie turned reporter was sacked by the ABC in May following an internal investigation into his podcast appearance with former underworld figure Ryan Naumenko last year.

Mr Fazal took to social media to hit back at his former employer, insisting the very access he was now being criticised for was the reason he was hired in the first place.

“I've been trying to stay quiet and do my own thing and … just move on with my life,” he wrote. “But they just keep going on attacking me, my work, my sources and apparently I'm the one that's betrayed the ABC. I mean seriously.”

“My access to these kinds of sources is why they hired me. They've said it themselves. They used me to tell the kinds of stories they wanted.”

The scandal has already drawn blood from within the ABC's own ranks, with Media Watch turning the spotlight on the broadcaster's handling of the affair in a remarkable public act of self-examination.

Ms Puccini's exit marks the most senior scalp to date in a crisis that shows no sign of abating, and leaves a question mark over the future direction of the ABC's investigations unit at a time when its credibility is under the closest scrutiny in years.