Police will investigate claims of phone hacking in Scotland, the Crown Office has said.
They are also investigating whether witnesses lied during the perjury trial of Tommy Sheridan last year.
The Crown has already asked Strathclyde Police to make a "preliminary assessment" of the available information and the evidence given by certain witnesses in Sheridan's trial in light of allegations made against the News of the World newspaper.
They did not say which witnesses are being investigated but former News of the World editor Andy Coulson, Scottish News of the World editor Bob Bird and reporter Douglas Wight all gave evidence.
A Crown Office spokesman said: "Strathclyde Police have now reviewed the available information and following liaison with the area procurator fiscal at Glasgow, the Crown has instructed an investigation should commence. The investigation will be progressed expeditiously and in close liaison with the area procurator fiscal and Crown counsel.
"Significant resources will be deployed, though these will vary with the needs of the investigation."
Police will investigate allegations that witnesses gave false evidence in the perjury trial and whether data protection laws have been broken and whether personal data was illegally accessed in Scotland.
It will also look at any offences uncovered in material held by Metropolitan Police connected to phone hacking, as well as allegations of police corruption.
Following the investigation, Strathclyde police will report to the area procurator fiscal in Glasgow and Crown counsel.
Mr Coulson was called as a witness to the Sheridan trial in December 2010.
Mr Coulson, then Downing Street director of communications, told the trial in December that he had no knowledge of illegal activities by reporters while he was editor of the newspaper.
He also claimed: "I don't accept there was a culture of phone hacking at the News of the World."
Sheridan was ultimately jailed for three years in January after being found guilty of perjury during his 2006 defamation action against the newspaper.
He successfully sued the newspaper over claims that he was an adulterer who visited swingers' clubs.
Earlier this month it emerged Mr Coulson had hired one of Scotland's top QCs, Paul McBride.
Mr McBride represented Gail Sheridan, the wife of the former Scottish Socialist Party leader, in the trial.
She was acquitted of lying to the courts in her husband's successful defamation action against the News of the World in 2006.