SIX million documents will be examined in the inquiry into the Edinburgh trams overspend.

Speaking at the first official hearing yesterday, inquiry leader Lord Hardie outlined the extent of the probe that was set up by the Scottish Government after the much-delayed trams project soared to £776 million and had just one line from the airport to the city centre rather than three.

Hardie sparked an immediate controversy when he appeared to question the decision of Edinburgh City Council on August 20 not to revive its former arms-length company Transport Initiatives Edinburgh (TIE) because it would cost too much.

He said: “It appears that there is clear scope for a conflict of interest between the City of Edinburgh Council and TIE.

“This is not least because the council has raised an action for damages in the Court of Session against TIE, which has separate solicitors, albeit I presume funded by the council, but that’s perhaps something that can be clarified.

“If councillors were not fully advised of the correct position, it might be prudent of the City of Edinburgh Council to reconsider these issues following a full and more balanced report than the one which was available on August 20 in an effort to reduce any challenge that might impede this inquiry.”

Hardie also raised the issue of conflict of interest in relation to the law firm Pinsent Masons.

He said: “As I have already mentioned there is clear potential for a conflict of interest between the City of Edinburgh Council and TIE, however there would also appear to be a potential conflict of interest involving Pinsent Masons. That potential arises in different waysThe firm is acting for TIE in a legal action against tram contract lawyers DLA Piper Scotland LLP while acting against TIE in the legal action pursued by the council.

Pinsent Masons is representing both the council and contractor Bilfinger Construction UK Ltd at the inquiry, raising issues of confidentiality and loyalty.

Lord Hardie said: “I want to be satisfied that both of these have been addressed to avoid any risk of challenge to the inquiry.”

But lawyers representing the council and Bilfinger said disputes between the parties had been resolved and both will have separate legal teams from Pinsent Masons.

Hardie announced the “core participants” for the inquiry. They are the City of Edinburgh Council, Scottish ministers, contractor Bilfinger Construction UK, Carillion Utility Services, Siemens, DLA Piper Scotland LLP and designer Parsons Brinckerhoff.

He asked each of the core participants to consider conflict of interest and provide written responses to the inquiry by November 27.

“This inquiry cannot determine whether anyone is guilty of an offence or is liable to pay damages to someone else," said Hardie. "Having said that, others might choose to draw inferences about such matters from findings in fact made in the report submitted to Scottish ministers and based upon evidence evaluated by me."

“I have a responsibility to ensure that the inquiry is carried out in an independent, fair and effective manner.

“My obligations are to the public as a whole.”

Andrew Kerr, chief executive of the City of Edinburgh Council, said: “We welcome today’s Preliminary Hearing and the progress made with the Inquiry so far. The Council has fully committed to playing a full and active role in the Inquiry, as a Core Participant.

“We have cooperated fully with Lord Hardie and his team as the process has developed, making available all information and documentation relating to the Council and to TIE and their involvement in the project.

“While we fully support the aims of the inquiry, the council is also mindful of the potential impact on the taxpayer. In August 2015 , the council decided it was not willing to fund the revival of TIE to take part as a core participant in the inquiry, and this still stands.

“TIE is a dormant company with no funds to meet any costs of representation at the inquiry, which would have to be borne by the public purse. As the shareholder of TIE, the council has committed to speaking for and on and on behalf of TIE as the inquiry proceeds."