SCOTS Tory Party leader Ruth Davidson has been interviewed by police in her Parliament offices in connection with allegations pro-Union campaigners illegally counted postal votes in the weeks before independence referendum ballots closed.

Ms Davidson was spoken to yesterday, six days after Police Scotland was instructed to carry out an investigation into alleged electoral secrecy law breaches.

Party sources say the interview was conducted on the basis of her being a witness and that Ms Davidson is not the subject of the investigation.

The formal police probe was sparked after the Scottish Tory leader said on a televised discussion that postal vote "tallies" were being taken in the weeks before the referendum ballot closed at 10pm on September 18.

Police made initial telephone contact with Ms Davidson last Friday and party sources said at the time, and continue to say, that there is "no suggestion she was accused of doing anything wrong".

Central to the probe is televised coverage of the referendum results, 45 minutes after the polls closed, in which Ms Davidson said that the No camp had been incredibly encouraged by the results of a "sample opening" of the postal ballot that she said had taken place around the country during the few weeks prior to the poll.

Complaints over her account of the postal vote "tallies" raised concerns the information may have helped inform the No campaign's decision to issue the vow of more powers for Scotland from the three main party leaders.

A Scottish Conservative Party spokesman said yesterday: "Ruth had arranged to speak to police today in her office to help them with complaints they had received."

In the footage forwarded to police, Ms Davidson said: "Postal votes are going to be enormously important in this campaign; about 18 per cent of the vote is going to come out of postal ballots and we have had people at every sample opening, around the country, over the last few weeks, while that's been coming in. And we've been incredibly encouraged by the results."

Later, referring to postal ballots, she said: "Different local authorities have had openings around the country", before adding: "There's people in the room that have been sampling those ballot boxes that have been opened and have been taking tallies and the reports have been very positive for us."

Political agents and campaigners are allowed to oversee the postal vote opening sessions, where checks are made to verify the signatures and dates of birth on postal voting statements against computerised records, but it is illegal to attempt to ascertain how a vote has been cast.

A Police Scotland spokeswoman said of the latest development: "We never comment on anyone who is spoken to as part of any ongoing investigation."