The independent review into the loan charge has been put on hold until after December's General Election.
The review was commissioned by Chancellor Sajid Javid in September, and is being led by Sir Amyas Morse, formerly head of the National Audit Office (NAO).
The loan charge, which came into effect on 6 April this year, added a 45% non-refundable charge on all loans advanced through the schemes, unless the individual had agreed with HMRC to settle their tax affairs by 5 April. The charge will affect at least 50,000 people who used loan-based avoidance schemes.
The All-Party Parliamentary Group (APPG) that is looking into the loan charge has published a survey of more than 2,000 people who face the charge. It found that 40% had seriously considered suicide, while a third have sought medication or counselling.
On 5 November, Jesse Norman, the Financial Secretary to the Treasury, asked Mr Morse to delay the publication of the review. HMRC has set a January 2020 deadline for settling claims under the loan charge, prompting concerns that the review will now not be made public in time.
Writing to the Chancellor, MPs in the APPG said: 'It is deeply worrying, considering the mental state that many thousands of people are in and with the impact on their families, that we now have a wholly unreasonable situation where people now cannot know whether or not they will face life-changing bills in January.'