He was held on suspicion of "conspiring to commit misconduct in a public office," the Metropolitan Police said.
He was questioned by police but has not been charged and has been bailed until February. He denies any wrongdoing.
It is believed to be connected to the arrest of a man suspected of being a Home Office whistleblower.
Series of leaks
The BBC understands that a junior Home Office official was suspended from duty 10 days ago over a number of leaks and the matter was referred to police. He was arrested but not charged.
It follows a series of leaks, including:
- The November 2007 revelation that the home secretary knew the Security Industry Authority had granted licences to 5,000 illegal workers, but decided not to publicise it.
- The February 2008 news that an illegal immigrant had been employed as a cleaner in the House of Commons.
- A whips' list of potential Labour rebels in the vote on plans to increase the pre-charge terror detention limit to 42 days.
- A letter from the home secretary warning that a recession could lead to a rise in crime.