When the £100,000 threshold was first introduced in 2010, it caught fewer than 600,000 people – or 1.9pc of all taxpayers. This has now risen to 5.6pc.
If the threshold had risen with inflation, it would now stand at £160,000, rising to £174,000 by 2031.
A separate survey by IG found that 92pc of workers earning between £90,000 and £125,000 with nursery-age children said that tax and financial pressures prevented them from investing enough to build future wealth.
More than half of those surveyed said they would immediately invest more if crossing the £100,000 threshold did not mean losing childcare support.
The Treasury was approached for comment.
