The leader of the Labour backbench tax revolt has threatened to restart the rebellion if Prime Minister Gordon Brown did not make clear exactly how he would compensate the losers from the scrapping of the 10p rate.
And former minister Frank Field warned that rebels were ready to block the Budget unless ministers made it "crystal clear" that those affected would be adequately recompensed.
He warned that this month's by-election in Crewe and Nantwich - and the very future of the Brown administration - were at stake if the Government failed to convince voters that they would not lose out.
Mr Field blamed much of Thursday's backlash against Labour in the local elections on the 10p row, warning that voters did not know whether they would be covered by the compensation package announced by Chancellor Alistair Darling and, anyway, did not trust the Government to deliver.
Mr Field withdrew an amendment to the Finance Bill challenging the abolition of the 10p rate last month after receiving assurances that the package for low-paid workers and pensioners aged 60-64 would be backdated to the start of this financial year, when the change came into effect.
But he said that Mr Darling's explanations of how the tax change would be "offset" by enhanced payments under the winter fuel allowance, tax credits and minimum wage had been "clear as mud".
Mr Field said he would table a parliamentary motion when the Commons returned after the Bank Holiday, calling for an explanation of the compensation measures, how many people would benefit and how much they would get.
"I, along with a number of MPs, believe that if ministers fail to make crystal clear how the package is taking shape, we should retable our Commons amendment on the 10p tax rate, and so block the Budget," he said.
"If the amendment were to be approved, it would prevent the Government from abolishing the 10p rate."
