Headed by Lord Strathclyde, former Conservative leader of the House of Lords, the group was meant to issue an initial report on extending devolution this autumn, with a final plan due out before the 2014 independence referendum.
But the party last night admitted the first report had been pushed into next year, and there was no confirmed date for its release.
The SNP said the leisurely pace showed the new Tory enthusiasm for devolution was skin-deep.
The hold-up is deeply embarrassing for Davidson, who marks her second anniversary as Scottish Conservative leader tomorrow.
It also emerged that Lord Strathclyde is only now getting round to consulting the Scottish Tory membership on greater devolution.
In a letter to party activists last week, he invited them to give their views at the party's convention in Dunblane on November 16.
The delay to the interim paper comes after private complaints about Lord Strathclyde's multiple commitments. Within three months of agreeing to head Davidson's Commission, the peer took on five paid part-time jobs.
One senior Tory said the timetable had been "shot to pieces". They said: "It's a cause for concern. It's crucial we produce an interim report as soon as possible to show people that if they vote No next year there is a policy platform for further devolution. The party needs to get a grip and ensure there's no more slippage."
Davidson announced the Strathclyde Commission in a speech in March entitled Strengthening Devolution, Taking Scotland Forward.
She said the Tories were "committed to a new path; more responsibility for the Scottish Parliament and a strengthening of devolution".
She gave a "commitment ... that we will publish our detailed plans in advance of the referendum, so the people of Scotland know exactly what we are proposing when they vote. Our working group will aim to produce an interim report this year so we will be able to show real progress is being made."
SNP MSP Linda Fabiani said: "This foot-dragging from the Tories underlines that for Scotland to achieve the powers we need is to vote Yes. Their hearts clearly aren't in it."
A Scottish Conservative spokesman said: "Given the level of interest, the report will now be next year to ensure the consultation and engagement is as wide as possible."