POLICE Scotland is under fire after new figures show a surge in the number of spying orders giving officers access to people's emails and telephone records.

More than 19,000 requests were approved "in-house" last year by senior officers, up 5% from the year before the single force came into being. However, Police Scotland is refusing to say how many times it has asked the Scottish Government to approve controversial interception warrants, which allow officers to listen in to phone calls.

The Regulation of Investigatory Powers (Scotland) Act 2000 (RIPSA) and UK legislation governs the way police forces and other bodies carry out surveillance and snooping against suspects, or people caught up in criminal investigations.

Police forces have been criticised for using the powers to uncover journalists' sources, while the security services have also snooped on lawyers representing clients.

Two main options are available to Police Scotland and other agencies.

An interception warrant, which must be approved by the Scottish Government, allows officers to read emails and listen to calls.

The other route is for agencies to get internal approval for "acquiring" emails and other data, permitting bodies to examine when and to whom communications were sent, but not to inspect the content.

For Police Scotland, superintendents either approve or reject applications.

Under freedom of information legislation, the Sunday Herald asked for the number of interception applications made by Police Scotland to the Scottish Government, compared to the old territorial forces.

The same question for in-house approvals - comparing Police Scotland to the last year of the legacy forces - was also tabled. However, Police Scotland has refused to reveal how many surveillance applications were made to the Government on the grounds that disclosure is "prohibited".

The force also initially refused to "confirm or deny" holding ­information about in-house approvals, noting that, in any case, such a disclosure would be exempt under national security, law enforcement and environmental provisions.

It argued that "the very act of confirming or denying that intelligence exists would set a precedent".

After an appeal to the Scottish Information Commissioner, Police Scotland last week reversed its opposition to revealing the in-house figures. For 2013, 19,390 RIPSA authorisations and notices were granted internally by the force. In the previous 12 months, the figure was 18,382.

Police Scotland's opposition to releasing basic information on the scale of its snooping operations could appear odd, as some statistics were already in the public domain.

The watchdog for monitoring RIPSA revealed the 19,390 figure in its latest annual report, although a comparison with the previous year was not disclosed.

Statistics showing the total number of interception warrants granted by ministers between 2008 and 2010 have also been published.

Meanwhile, all chief constables in the UK have been asked by the Interceptions of Communications Commissioner to provide details of all in-house approvals relating to journalists and their sources.

Asked whether Police Scotland had used these powers for such a purpose, a spokesperson said: "Police Scotland has not used Part 1 Chapter 2 RIPA powers to acquire communications data to identify journalistic sources."

Scottish Liberal Democrat justice spokesperson Alison McInnes MSP said: "There is no rhyme or reason as to why this information should not be made public. People deserve to know the extent to which ministers are sanctioning police interceptions of public communications."

Graeme Pearson, a former senior police officer and now Scottish Labour's justice spokesman, said: "The release of information regarding the scope of interception and the gathering of communications intelligence can be useful to those being targeted, whether for terrorism or organised crime. Nevertheless, silence is no answer.

"Justice Secretary Kenny MacAskill must find the means to assuage public concerns while at the same time protecting the very sensitive nature of this work."

A Police Scotland spokesperson said: "These powers are lawful and used for a variety of purposes, from missing person enquiries to tackling organised crime and other major investigations, with the purpose of keeping people safe."