Sir Keir Starmer has called for Labour's inquiry into a leaked anti-Semitism dossier to be concluded in a "matter of months", ahead of a meeting of the party's ruling National Executive Committee.
The NEC will convene later on Thursday to set the timescale and frame of reference for the probe into the leaking of the 860-page report that reignited divisions as the new leader tries to unite the party.
The document found "no evidence" of anti-Semitism being handled differently from other complaints and that "factional opposition" towards Jeremy Corbyn hindered efforts to tackle the crisis.
Labour insisted it takes data protection "extremely seriously" after suggestions that legal action could be taken against the party by people named in the report.
Sir Keir's spokesman said: "The NEC is meeting tomorrow and at that meeting they will agree the terms of reference for the inquiry.
"Keir has made it clear that he wants it to be a swift investigation."
Pressed on how quick, the spokesman replied "a matter of months" and said it was for the NEC to determine.
"That's his objective as part of rebuilding the Labour Party and improving trust. There will be more clarity tomorrow," the spokesman said.
Labour said officials are working with the Information Commissioner's Office (ICO) over the leak and insisted it takes its responsibility on data protection "extremely seriously".
"We're continuing to work closely with the ICO and taking an extensive number of steps to safeguard both the data and welfare of staff and members," a spokeswoman added.
Allies of Mr Corbyn, who resigned as leader after Labour's historic general election defeat, said the document showed that elements of the party undermined his leadership.
Sir Keir received a report into all the outstanding allegations of anti-Semitism in the party after meeting Jewish leaders, his spokesman said.
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In contrast to Mr Corbyn receiving unprecedented criticism from Chief Rabbi Ephraim Mirvis during the 2019 election, Sir Keir has won praise for committing to root out the problem.
