Shares in commercial litigation funding titan Burford Capital plunged on London's AIM exchange on Wednesday, in response to a report from short-selling investment firm Muddy Waters Research.

Muddy Waters, which conducts investigative research on publicly-traded companies and takes investment positions that reflect its findings, called Burford "a poor business masquerading as a great one", concluding the company is "arguably already insolvent".

In response to the news and Muddy Waters' actions, shares dropped by 64% at one point in trading, before rallying in the late afternoon. At close on Wednesday, they were trading at 600 pence after starting the day trading at 1,130 pence.

"BUR is a perfect storm for an accounting fiasco," the report said. "It is a fund that invests in an illiquid and esoteric asset class, which few investors can understand well."

Muddy Waters specifically alleged in a 25-page report that Burford has been manipulating its metrics for returns on invested capital and internal rate on returns, by aggressively overinflating the value of cases in its investment portfolio.

It listed seven specific techniques Burford purportedly uses to misrepresent its actual returns, including categorising losses as wins, counting awards or settlements with uncertain to highly unlikely collections as "recoveries" equivalent to cash returns, choosing its own cost denominator in cases with recoveries when the total cost is much greater, and delaying the reporting of trial losses for two years.

Muddy Waters also called Burford's governance structures "laughter-inducing", noting that CFO Elizabeth O'Connell is married to CEO Chris Bogart.

"Under the best of circumstances, this should alarm investors; however, with a company that consistently books non-cash accounting profits, it is unforgivable," it said.

And it also flagged Burford's presence on the AIM exchange, the London Stock Exchange's international market for smaller growing companies, as cause for concern, noting that the company's disclosure requirements are lighter than they would be for the main exchange, "and far lighter than they should be".

The attack comes two weeks after Burford released its financial results for the first half of 2019. While the company touted record gains, shares dipped by 6% following the release of the numbers. At the time, Bogart pinned the movement on long-term investors looking to cash out.

Burford's board of directors acknowledged the "short attack" report on Wednesday, saying the company had not been contacted by Muddy Waters and that the blitz was entirely unexpected.

In a statement, the company asserted that its cash position and access to liquidity were strong, with more than $400 million of cash and cash equivalents on hand as of August 5.

Burford also defended its accounting standards. While Muddy Waters said the company woos investors with such metrics as "returns on invested capital" and "internal rate on returns" that fall outside of International Financial Reporting Standards (IFRS), Burford said it uses the same IFRS accounting that is used widely across the financial services industry and has received clean audits from Ernst & Young every year since 2010.

Burford added that it provides line-by-line details on every investment it makes, noting that it updated its website with its latest reporting on Tuesday.

"We are transparent about how we analyse and report on that data; our approach has been consistent for many years," the company said.

Burford's share price initially dipped late on Tuesday, a development the company connected to rumours of a short sale. Before the release of the Muddy Waters document, the company said that it had brought in market experts and experienced outside litigation counsel to investigate any potential misconduct. Burford's website lists Magic Circle firm Freshfields Bruckhaus Deringer as its primary adviser on U.S. and English law.

"Short sellers of this ilk are not long-term investors," the company stated. "Rather, their goal is to panic investors into selling their holdings and thereby to drive down the share price. If investors oblige them, then the attack succeeds, long-term investors are harmed and the short sellers pocket a quick payday."