Special branch detectives from Scotland Yard questioned him and Tony Clarke, the former Labour MP for Northampton South, about alleged breaches of the Official Secrets Act.
David Keogh, a former cabinet office communications specialist, has been charged under the Official Secrets Act with sending the memo to Leo O’Connor, a researcher for Clarke. Both men face trial at the Old Bailey later this year.
Senior CPS lawyers are now in the final stages of deciding whether to press charges.
A spokesman said: “A decision on Kilfoyle and Clarke is expected soon.”
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