She came under fire after it emerged earlier this week that she had been appointed as senior adviser at Tulchan Communications, being paid £50,000 a year for 24 days’ work.
It has also emerged she has set up her own management consultancy, Kirkholm Broadlands Ltd.
Broadcaster John Morrison, of the Public Relation and Communications Association, said: “The umbrella organisation that governs the lobbying industry is quite clear on this, that it is a conflict of interest, that companies should not hire parliamentarians. If you think about it, you can’t be lobbying or working for a company that lobbies to change the law and vote on law changes at the same time.”
And Lothians Green MSP Alison Johnstone called for Ms Davidson to step down so a by-election could be held.
She said: “The people of Edinburgh Central elected Ruth Davidson to represent them, not use her position to earn £50,000 from lobbyists.
“This is clearly a conflict of interests. Davidson needs to resign from the corporate body and as an MSP so Edinburgh Central can elect a committed representative.”
He said: “She has been hired at £50,000 for 24 days a year. There are many people in her constituency who won’t get £50,000 for two or even three years’ full-time work and she has taken this as an additional job. It’s another example where people will be completely cynical about the political class.”
Edinburgh Pentlands SNP MSP Gordon MacDonald said MSPs were bound by strict rules on accepting cash to raise issues on behalf of outside groups and were banned from being paid to advise on parliamentary affairs.
He said: “People will wonder how Ruth Davidson can stay within the letter and the spirit of these rules if raising matters related to any of her employer’s clients, of which there are many. In fact, the scale of Tulchan’s client list is so large it’s hard to see how Ruth Davidson can raise almost any issue in parliament without facing a potential conflict of interest.
“If Ruth Davidson isn’t willing to focus on her role as an MSP she should allow the people of Edinburgh Central to pick a representative who is. ”
Ms Davidson has made it known her new job is “specifically, legally and contractually not a lobbying role”.
And a Tory spokesman has said the new post is “well within all parliamentary and industry rules”, adding she was committed to seeing out her term as MSP for Edinburgh Central.