The Edinburgh Central MSP, who stepped down as leader in August and is expected to quit the Scottish Parliament at the next election in 2021, has been appointed a senior adviser at Tulchan Communications.
The post will see her paid £50,000 a year for just 24 days of work.
It has now emerged Ms Davidson set up a management consultancy called Kirkholm Broadlands Ltd with her partner Jen Wilson on October 14, but did not mention it when she announced her work with Tulchan, The Herald reports.
Papers filed with Companies House show Ms Davidson and Ms Wilson registered as directors and shareholders of the new entity when it was incorporated 11 days ago.
A Scottish Conservative spokesman told The Herald, Ms Davidson had set up the business “as a way of separating this work from politics, as many other politicians do”, and claimed it had no bearing on her plan to stay on as an MSP.
The spokesman continued: “Ruth’s business advisory role is well within all parliamentary and industry rules.
“It is far less onerous than the party leadership she held for eight years, and she is able to complete the 16 hours a month it requires while still having more time for her family and constituency. Ruth is committed to seeing out her term as the MSP for Edinburgh Central.”
Earlier this week, industry body the Public Relations and Communications Association said there was a clear potential conflict of interest for the former party leader to hold her post with Tulchan and argued it was wrong for lobbying agencies to employ legislators.
PRCA director general Francis Ingham said: "The possible conflict of interest in doing so is clear, and damages the reputation of both our industry, and of the political process.
"PRCA members are prohibited from employing parliamentarians - and with good reason. Unlike the majority of its competitors, Tulchan is not a PRCA member. But in the public interest, we would nonetheless urge them to reconsider this appointment."
Tulchan's managing partner is Tory fundraiser and former Conservative Party chairman Andrew Feldman, now Lord Feldman of Elstree.
He said: "We are delighted that Ruth has chosen to join Tulchan as a senior adviser and look forward to having her on board."