Documents relating to the banking crisis have gone missing at the Department of Finance.

The department has conceded that some correspondence forwarded from Bank of Ireland to former minister for finance Brian Lenihan can no longer be located.

It says it has started a process to ensure the integrity of its records ahead of the banking inquiry.

In 2009, the department was asked under Freedom of Information to release copies of all correspondence between the late Mr Lenihan and the chief executives of the banks during the period August 2008 to March 2009.

The department released eight items.

Late last year, Sinn Féin finance spokesperson Pearse Doherty requested repeat copies of these documents.

He was told that two out of the eight could no longer be found.

When released in 2009, both had been completely redacted.

They concerned correspondence between the governor of Bank of Ireland Richard Burrows and an advisor to the Jupiter group, Noel Corcoran.

Jupiter was trying to buy Bank of Ireland at the time.

Mr Doherty said the fact that the department could not locate records was worrying ahead of the banking inquiry.

He said it raised questions as to whether other documents may have gone missing.

In a statement to RTÉ News this evening, the Department of Finance said it had carried out a widespread search for the documents and it was not clear why the original versions could not be located.

It said that it had undertaken a project which would ensure the completeness and integrity of its records from the time of the bank guarantee.

It said it was also considering the feasibility of improving its "records management procedures and processes".

It said that it was not aware of any documents relating to the bank guarantee which may have gone missing.

Mr Doherty said: "These letters existed in 2009.  They were released but the content was fully redacted to a journalist under the Freedom of Information legislation.

"However I have now been informed that these letters have gone missing from the Department of Finance.

"These are some of the only documents between the Governor of the Bank of Ireland and the Minister for Finance during a period when the government decided to pump €3.5m of taxpayers' money into that bank."

He went on to say: "The only reason we know that these documents are missing is because two separate FOIs were made on the same document over a four year period.  The question has to be asked about what other sensitive documents have gone missing.  The reality is that we may never know.

"If the upcoming banking inquiry is to be successful it is important that all relevant documents are found or returned."