The top civil servant at the Department of Finance has said there has been no investigation into the increased trade of SiteServ shares just before it was sold.

Derek Moran says dealing with insider trading is the responsibility of the Stock Exchange, but not for the government.

Mr Moran was giving evidence at the Banking Inquiry where it emerged the Department doesn't know how much IBRC's liquidators will charge for the inquiry into how SiteServ was sold.

Figures from the Department of Finance attended a hearing of the Public Accounts Committee (PAC) this afternoon.

Mr Moran told TDs it wasn't up to him to investigate the reason why so many SiteServ shares were sold just before the company was sold off.

“This alleged spike happened before the department had any visibility on the Siteserv transaction at all,” Mr Moran said.

“To date this is still an allegation of which I’m not sure there is any evidence,” he added.

The Department of Finance has been accused of writing a 'blank cheque' for the inquiry into the sale of SiteServ.

The claims come as the department admits it cannot estimate how much it will have to pay IBRC liquidators to undertake the inquiry.

Sean Fleming of Fianna Fáil said he was stunned to learn that there was no budget for the initial inquiry into how SiteServ was sold.

The company was sold to Denis O'Brien's Millington by IBRC in 2012 at a loss to the taxpayer of over €100m.

The sale is now the subject of special investigation, and the PAC is exploring the broader relationship between the department and IBRC.