WASHINGTON, March 2 (Reuters) - A controversial plan by U.S. Senate Republicans to make President Donald Trump’s 2017 tax cuts permanent by ignoring the cost to the deficit is raising warnings from party fiscal hawks and independent analysts of a potential “debt spiral” that could undermine economic growth.

Top Senate Republicans, including Majority Leader John Thune, are determined to make permanent tax cuts due to expire at the end of the year, through a parliamentary maneuver that bypasses Democratic opposition. Because rules prohibit bills from expanding the deficit beyond a 10-year window, they intend to ignore a projected revenue loss of more than $4 trillion by claiming that tax policy would remain unaltered.

The ploy is already running into opposition from enough hardline Republican fiscal conservatives to prevent such a measure from making it through Congress, given that the party holds only a 218-215 majority in the House of Representatives.

“I can’t support that. It’s just a way to break the bank,” said Representative Thomas Massie, a Kentucky Republican who is one of the leading deficit hawks in Congress.

Two other fiscal conservatives, Representatives Victoria Spartz and David Schweikert, signaled opposition as well, while others said they saw the plan as a way to avoid offsetting Trump’s tax priorities with deep spending cuts.

“It’s heresy. They’re being absolutely intellectually disingenuous,” said Schweikert, of Arizona. “This is their way of avoiding making difficult decisions on modernization and changing the spending curve. I view it as absolutely immoral.”