In the run up to November's midterm elections, President Donald Trump promised a vague middle class tax cut that he has barely mentioned since.

His Treasury secretary, Steven Mnuchin, will not say whether it was a real proposal.

"I'm not going to comment on whether it is a real thing or not a real thing," he told Bloomberg in an interview Tuesday. "I'm saying for the moment we have other things we're focused on."

In late October, Trump floated a 10 percent tax cut for the middle class in addition to the tax reform plan Republicans passed last year. He pledged to introduce a "resolution" before the Nov. 6 midterm elections, catching Republican congressional leaders and even White House officials off guard.

The proposal came as Republicans struggled to make their tax overhaul — the main achievement during two years of Republican control of Congress and the White House — a winning issue on the campaign trail.

Democrats hammered GOP House members over the tax plan, saying it benefited corporations and the wealthy more than working and middle class Americans. Democrats also argued Republicans would use the deficits generated by the tax cuts as an excuse to slash Social Security and Medicare benefits. Challengers in affluent, high-tax areas where many taxpayers saw their state and local tax deductions capped also criticized that portion of the Republican law.

Trump's vague proposal days before the elections in part aimed to alleviate those concerns. So did a second round of Republican tax changes that passed the House earlier this year, which in part made individual tax cuts passed as part of the GOP plan permanent. The Senate has not yet taken up the bills.

House Republicans lost 40 net seats and their majority in November. When Democrats take control of the chamber next month, they plan to attack the tax law.

Read the full Bloomberg story here.

Subscribe to CNBC on YouTube.