Richard Desmond's Express Newspapers continued using convicted private investigator Steve Whittamore until as late as July 2010, the Leveson Inquiry heard this morning.
The company's legal chief Nicole Patterson was also unable to say whether Express Newspapers still employs the service of Whittamore, who was found guilty of obtaining and disclosing information under the Data Protection Act in 2005.
The inquiry heard that an internal audit found the last invoice for Whittamore's company JJ Services was dated 31 July 2010, while the earliest invoice was from 31 January 2005 - nine months after he received a conditional discharge at Southwark Crown Court.
When Whittamore's home was raided in March 2003 police seized a cache of handwritten records documenting thousands of requests for information from journalists, including ex-directory telephone numbers, home addresses, 'friends and family' telephone numbers and criminal record checks.
Appearing at the inquiry after Patterson, the editor of the Daily Star, Dawn Neesom, said she had only discovered today that the paper was using Whittamore's firm in 2010 and admitted it was a cause for concern.
Neesom said she will discuss the issue of search agents and private investigators with legal and finance executives at the company, adding: "Systems can always be improved and this is one of them."
Patterson told the inquiry that Express Newspapers began an internal investigation into phone-hacking and the use of private investigators on 26 July 2011, which looks at records dating backing to 2000.
So far it had not discovered any evidence 'suggesting anyone was doing phone-hacking or anything of that nature".
They were particularly concerned with large or unexplained payments, she said. The highest such payment discovered so far was for around £1,500 or £1,600.
A 'cloud hanging over' Whittamore
Patterson confirmed that the investigation did not involve any formal interviews with journalists, telling the inquiry that she instead spoke with news editors and editors to find out the names of search agents and private investigators that the group's newspapers had used.
During the course of her investigation one of the names that came up was JJ Services, but when asked if the company was still using them she replied: 'I don't know the answer to that."
Asked if she knew what methods JJ Services used to find out information - and whether they were legal - she said: 'I don't."
The counsel to the inquiry, Robert Jay QC, said that 'at the very least there's a cloud hanging over'Whittamore due to his conviction, and pressed Patterson on why the company had not investigated his company.
'It's not something that's within my remit I'm afraid,'she responded, claiming that it was instead an issue for the editors.
The lawyer said that Express Newspapers used four other search agencies - Express Locate, Longmere Consultants, Searchline and System Searches - to provide journalists with information such as addresses and phone numbers.
She believed they were "totally legitimate" companies, telling Jay: "I'm not sure that when you employ anybody, that you ask in great detail how they go about doing what they do," she said.
"You employ a company to do something for you and you expect that they would do it within the law."
An audit by the company revealed that the group spent around £115,000 on search agencies over 10 years, compared with £9 million on pictures in 2008 alone.