Prime Minister David Cameron's former director of communications Andy Coulson has been charged with perjury.
Mr Coulson, 44, was questioned in Glasgow as part of an investigation into evidence at the perjury trial of former MSP Tommy Sheridan in 2010.
He was detained at his south London home on Wednesday by Strathclyde Police and formally arrested that evening.
The ex-News of the World editor was a Downing Street employee at the time he was a witness at Glasgow's High Court.
Mr Coulson was detained at his south London home at 06:30 BST on Wednesday. He arrived at Govan police station shortly before 15:30 BST and was held for about six hours before being released.
A Crown Office spokesman said there was no legal obligation for Coulson to stay in Scotland, and he was free to return to his home in London.
The spokesman said no date had been set for any court appearance.
A decision will now be taken by Scotland's prosecution service, the procurator fiscal, about whether Mr Coulson should face a trial.
Earlier, a police spokeswoman said: "Officers from Strathclyde Police's Operation Rubicon team detained a 44-year-old man in London this morning under section 14 of the Criminal Procedure Scotland Act 1995 on suspicion of committing perjury before the High Court in Glasgow."
Mr Coulson gave evidence at the trial of former Scottish Socialist MSP Tommy Sheridan in 2010.
Sheridan was awarded £200,000 in damages from the News of the World in 2006 after it printed allegations that he had committed adultery and visited a swingers' club.
After the court action, the former MSP and his wife Gail were charged with perjury.
She was acquitted during the subsequent trial but Sheridan was convicted in December 2010. He has since been freed after serving just over a year of a three-year sentence.
Mr Coulson was called to give evidence at Sheridan's trial over two days as he was editor of the News of the World between 2003 and 2007.
During heated exchanges with Sheridan, who represented himself at the trial, Mr Coulson denied being involved in, or aware of, any illegal activities, including phone hacking.
Mr Coulson resigned from the post of Mr Cameron's director of communications in January 2011, saying coverage of the News of the World phone hacking scandal had "made it difficult to give the 110% needed in this role".
In July 2011, he was arrested by Metropolitan Police investigating the News of the World hacking scandal and later released on bail.
BBC chief political correspondent Norman Smith said: "Unlike the arrest of Mr Coulson last year by the London Metropolitan Police - which centred on claims about hacking during his time as editor of the News of the World - this arrest relates to a period when Mr Coulson was working as David Cameron's director of communications."