A top energy analyst has claimed the data provided by the whistleblower to Ofgem neither proves nor disproves any suggestion of rigging wholesale prices ahead of the winter months.
Patrick Avis told Huffington Post UK there were any number of reasons to explain the low prices submitted on the day which is being investigated by energy regulator Ofgem and the Financial Services Authority, ranging from a genuine attempt to rig the market to a simple typo.
"From what I have read it seems that the agency (ICIS Heren, which publishes energy pricing reports) was debating how best to reflect the prices and took a middle of the road approach," he explained.
"It's very easy to read manipulation into the market and to fit circumstances to fit a message; without seeing the next level of detail it's very hard to say for certain.
"As a roughly comparable example, whenever someone buys a TV on an electrical company's website for £1, they're clearly buying the TV well below market, but does that mean the retailer is trying to manipulate the market, or are their computer systems experiencing gremlins and someone is snapping up a bargain?"
The furore over wholesale energy pricing -and the alleged manipulation of price - came about after a 'whistleblower' from ICIS Heren told the FSA that Britain's £300bn wholesale gas market has been "regularly" manipulated by some of the big power companies.
Separately, the energy regulator Ofgem has been warned by ICIS Heren that it had seen evidence of suspect trading on 28 September, a key date as it marks the end of the gas financial year and can have an important influence on future prices.
A second gas price reporter, also from ICIS Heren, told the Guardian he had noted "half a dozen or a dozen" occasions that price differentials over the course of a year looked unusual, with one particularly marked case on 9 September 2011.
All six of Britain's big energy suppliers have denied any involvement in any alleged rigging, with several pointing the fingers to other players in wholesale buying markets.
EDF Energy said it "does not participate in loss-leading trading activity and considers it to be against existing market regulation...We make information likely to impact market price formation publicly available on our website."
Npower said: "There is an explicit commitment in our code of conduct to comply with all laws and regulations."
Scottish Power said that it had "never engaged in trying to fix wholesale gas trading markets", adding: "Our trading division always acts with integrity and follows all rules in all of its engagements with the market."
SSE said: "We are entirely confident that our energy portfolio management team operate in a fair and legitimate way."
E.On said: "We are confident that all of our colleagues always act in the correct manner and as a company we fully abide by all appropriate regulations."
And Centrica, which owns British Gas, said it had "very robust governance and compliance policies" which were regularly reviewed. "Centrica's traders are prohibited from providing price information to price reporting agencies," it added.
How are energy prices set?
There are two main ways in which wholesale gas prices are transmitted to the market.
The first is through an exchange, where people, companies or organisations meet to trade. Having everyone in one place increases the volumes of trades and should aid fair price discovery.
There are different exchanges but - just like with shares - people will tend to centralise around one - there are two London Stock Exchanges, for instance.
This is, according to energy analyst Avis, the most transparent, as although the trades can occur anonymously, the exchange can monitor and observe prices and therefore report an agreed market price.
"An exchange however will not in itself prevent manipulation, since there’s nothing stopping two counterparties agreeing off-exchange prices and then transacting on the exchange, but this breaks exchange rules," he added.
The second way is through contacting counter-parties - ie anyone involved in the buying process - to ask what trades they have done and at what price. These are know as Over-the-Counter trades or direct agreements between Company A and Company B with neither party required to make the details public.
"It's like you or I ringing supermarkets and asking the price of apples; we'd call ASDA, Tesco and Sainsbury's and get separate prices and find the average Apple price. It might be the Morrisons tells up that theirs are 20p cheaper and Harrods were £1 more expensive," explained Avis.
"To get a reflective price of what an Apple is worth we would remove Morrisons and Harrods from our average."
It is accepted practice that when asked, the OTC counterparty will give broadly indicative prices, with reporting agencies then taking averages of the prices, but the Libor scandal showed how the potential for participants to manipulate price quotes is a strong one and this is especially true in more illiquid products.
The Heren index is set at the last price a product was traded - so the accusation is that certain market participants looked to influence the market by making a series of very late trades.
In a blog posted on his site, Avis suggests there was no knock on effect for consumers.
"It is likely that no consumer would have directly have lost out. Indeed, one could argue that consumers were in it beneficiary of this since the market price is set at a lower level than it wouldn’t be without these trades. Why would someone want a lower market price the gas?," he wrote.
"Clearly, if you’re on the long side of the market, that is to say you’re buying the gas, it would be in your interest to see a lower price for that product."
But Seth Freedman, the ICIS Heren whistleblower, told the BBC that even if this alleged instance did not add to customers' bills, it was still damaging: "There's certainly a link. They [the power companies] are telling you: Look, in order to make our profits and cover our costs and so on, we have to give a price to retail customers which reflects the cost to us'.
"If you can't trust the market at a wholesale level, it becomes a crisis of confidence. People at retail level are just thinking, 'I don't trust these companies' - and it needs to be scrutinised."