From April next year Holyrood will have control over 10p of the 20p basic rate of income tax and by 2018 it is expected they will have control over all income tax on earnings.
However, the UK Government is refusing to publish a detailed review it carried out in March this year after HMRC progress reports have revealed that there have been “red alert” areas of concern including identifying Scottish income taxpayers.
Conservative Scottish Secretary David Mundell refused a request to publish the March report after a written question from his Labour shadow Ian Murray.
Then two further questions from Mr Murray asking for a summary of the key points and reasons for refusing publication have received holding answers which means nothing needs to come out until after the summer recess in September.
Mr Murray said: “They need to publish this report immediately. The new powers over income tax represent the biggest transfer of financial powers to the Scottish Parliament that has ever taken place.
“Instead of backroom meetings between the UK and Scottish Government they need to come clean about any problems we’re going to face in just a matter of months.”
But a UK Government spokesman said: “Preparations are on track to bring the Scottish rate of income tax into effect from April 2016 as planned, at which point the Scottish Government becomes responsible for setting the level.”