Dame Lowell Goddard quit as chairwoman of the national child sex abuse inquiry after panel members including the woman who succeeded her turned against her in an apparent power struggle.
Dame Lowell disclosed in a letter to MPs how she was forced into her sudden resignation in the summer after being confronted by colleagues she previously believed were loyal.
The account given by Dame Lowell of why she quit will put pressure on the new inquiry chairman Professor Jay - the fourth in two years- to explain her role in the resignation that plunged the £100 million ($169m) inquiry into crisis.
Amber Rudd, the Home Secretary, had previously told MPs that Dame Lowell had resigned because she was "homesick and lonely".
In an eight-page memorandum, Dame Lowell, a former New Zealand high court judge, said she was confronted in a meeting on August 4 after a series of adverse newspaper headlines and "widening personal attacks on me and my competence". She resigned a few hours later from her £360,000 a year job with an £80,000 pay off.
"I believe this is when the team lost their nerve about my ability to continue leading the inquiry," she wrote in the memo, "The pressure was relentless... On the morning of 4 August, three of the panel members came to see me. In discussion with me it became clear that I no longer had the support of my senior colleagues at the Inquiry that I would need if I were to continue as Chair."
Dame Lowell does not name the three panel members - out of a total of four - but it is thought Prof Jay, who took charge not long after, was one of them. The inquiry did not deny Prof Jay was at the meeting.
The memo suggests an ongoing struggle between Dame Lowell and Ben Emmerson QC, the counsel to the inquiry who has also since resigned, on the one hand and members of the panel to the Independent Inquiry into Child Sexual Abuse (IICSA) on the other.
Dame Lowell said in the months before she quit there had been ongoing tensions with panel members, including Prof Jay, wanting more control of decision making.
Dame Lowell said they had not understood that "important procedural decisions" could only be made by her as chairman.
She also said that criticism of her for working on the inquiry while in New Zealand was unfair since the Home Office had sanctioned her to do so despite the 13-hour time difference. "Working out of a foreign location was authorised so long as the environment was secure," said Dame Lowell.
She appeared to also accuse panel members of plotting behind her back. She said that the panel members had given "apparent support... throughout my tenure".
She had not known until a parliamentary select committee hearing last month that one panel member Drusilla Sharpling had complained about her 'leadership' behind her back to the then director general of the Home Office.
"For example, Drusilla Sharpling, in May/June and again in July, volunteered to me her absolute loyalty and support for me," she wrote.
Dame Lowell said she had also been wrongly subjected to criticism over the inquiry's investigation into Lord Janner, the former Labour MP accused but never convicted of child sex abuse.