The documents that the Serious Fraud Office (SFO) sent to the wrong person are linked to an investigation into the defence giant BAE Systems.
While it is not clear what the documents relate to, the SFO has investigated the company over contracts it won with several countries including Saudi Arabia, Tanzania and South Africa.
BAE Systems was fined $400 million (£257m) by the US and Britain in 2010 following long-running corruption probes into defence deals around the world.
Last year, the company paid £30 million to the Tanzanian population after failing to keep adequate records of payments it made to receive a defence contract in the country.
BAE Systems has said that it is "concerned" to hear of the data loss, but that it is "a matter for the Serious Fraud Office".
The defence giant also confirmed in a statement that the material was not sent to a current or former employee of the company.
We were concerned to hear of this unfortunate incident but understand it has now been dealt with by the relevant authorities. Ultimately, this is a matter for the SFO and as far as BAE Systems is concernedit is now closed.
The Serious Fraud Office (SFO) has said it appointed former security chief at the Palace of Westminster, Peter Mason CBE, to look into the data loss.
Mr Mason is said to have concluded that it was accidental, and made a number of recommendations which have all been accepted by the SFO.
Labour's Shadow Attorney General Emily Thornberry has described the accidental transfer of documents to the wrong person by the Serious Fraud Office as "incompetence of the first magnitude".
The SFO has stumbled from shambles to shambles, with the Attorney General completely failing to get a grip. It looks as if this blunder would never even have been revealed if he had not been compelled by Labour to divulge the information to Parliament. His account of what has happened raises more questions than it answers. How did this happen? What category of documents are we talking about here? Who received them by mistake? How much of the evidence has been destroyed? What is the Government doing to ensure that this never happens again?
Incompetence like this threatens to have an impact on the reputation of the UK and its relations overseas. People will be wondering how many other skeletons there are in the SFO cupboard that the Attorney General is aware of but is declining to make public. The Government needs to get a grip, get to the bottom of this mess and come clean about exactly what went wrong and how.
The Labour party has tweeted that the announcement from the Serious Fraud Office seems to suggest that up to 640 pages of evidence has still not been recovered.
Serious Fraud Office appear to admit up to 640 pages & other data is or could be still lost - http://t.co/Z7q7sbLN2I
The statement said that of the 32,000 pages of documents, 98 percent had already been recovered and that "efforts continue to recover all the remaining material that has not already been destroyed by the recipient".
The Serious Fraud Office (SFO) said that instead of returning thousands of pages of evidence to 59 different sources, it sent the entire batch of material to a single recipient.
The office said it had already contacted the 59 people involved and that it is "working to contact any others who may have been affected".
A statement from the Serious Fraud Office (SFO) relating to the accidental transfer of thousands of pages of evidence to the wrong person said:
The SFO has a duty to return material to those who supplied it, upon request, after the close of an investigation. In this instance the party requesting the return was sent additional material which had in fact been obtained from other sources.
The data constituted 3 per cent of the total data in the case. It consists of 32,000 document pages, 81 audio tapes and electronic media. Of this, 98 per cent of the material has been recovered and efforts continue to recover all the remaining material that has not already been destroyed by the recipient. No material relating to national security was included in the data.
The Serious Fraud Office says it has accidentally sent thousands of pages of evidence relating to an investigation into defence giant BAE Systems to the wrong person.
A statement from the office said it identified the data loss in May and that 98 percent of the material has already been recovered.
The office said that none of the material related to matters of national security.
I want to make it crystal clear that neither I nor the Board will tolerate improper business conduct of any sort and will take all necessary action to ensure compliance. This is a company with exceptional prospects and I will not accept any behaviour that undermines its future success.