WASHINGTON  In continued defiance of the White House, House Democratic leaders are readying a proposal that would reject giving legal protection to the phone companies that helped in the National Security Agency’s program of wiretapping without warrants after the Sept. 11 attacks, Congressional officials said Monday.

Instead of blanket immunity, the tentative proposal would give the federal courts special authorization to hear classified evidence and decide whether the phone companies should be held liable. House Democrats have been working out the details of their proposal in the last few days, officials said, and expect to take it to the House floor for a vote on Thursday.

The Democrats’ proposal would fall far short of what the White House has been seeking.

President Bush has been insisting for months that Congress give retroactive immunity to the phone companies, calling it a vital matter of national security. The Senate gave him what he wanted in a vote last month that also broadened the government’s eavesdropping powers.

But House Democratic leaders have balked at the idea.

When the White House would not agree allow more time for negotiations, House leaders last month let expire a temporary six-month surveillance measure. The White House says the Democrats’ inaction has imperiled national security. Democrats have accused Mr. Bush of fear-mongering.