Nicola Sturgeon is pushing ahead with her second independence referendum plans despite her most senior mandarin warning her they could hit her government's efforts to improve Scotland's public services, secret documents have disclosed.

Leslie Evans, the Scottish Government's permanent secretary, sent a "sensitive" memo to the First Minister stating she would provide an analysis of the "impact" of devoting civil servants to another separation vote instead of the SNP's domestic policy agenda.

She said she would "identify where we see scope for deprioritisation of activity" in the government's existing responsibilities, to free up the necessary manpower for dealing with Brexit and another referendum "in parallel".

In a remarkable disclosure, given Scots clearly rejected separation in 2014, Ms Evans said the work would include "transitional planning for moving to an independent Scotland."

Scotland's information watchdog ordered the SNP administration to hand over the memo to the Tories following a 13-month Freedom of Information (FoI) battle.

It was sent by Ms Evans on March 29, 2017, a few weeks after Ms Sturgeon tabled a formal request to Theresa May for the powers to stage another referendum, which was rejected by the then-Prime Minister.

But Ms Sturgeon is preparing to table another request before Christmas with the aim of staging a second separation vote next year, despite publicly claiming her priority is closing the huge attainment gap between rich and poor school pupils.