David Cameron will be forced to defend cuts to child benefit later amid Labour claims the key Government welfare reform policy was "unravelling" and expert warnings it could appear unfair.
Children's minister Tim Loughton said the move to axe the payments to 1.2 million families might need revising, just hours after it was unveiled by Chancellor George Osborne.
His comments came after criticism from unions and poverty campaigners and a warning from a respected economic thinktank that the cut could "seriously distort" work incentives.
Mr Osborne risked a backlash from middle class voters by announcing child benefit would be stripped from households with a parent who earns over around £44,000 from 2013.
He told the Conservative Party conference that the measure, intended to save around £1 billion in child benefit, was a "tough but fair" way to reduce Government spending.
When the country was struggling to pay down a structural deficit of £109 billion, wealthy families should not receive welfare payouts funded in part by the taxes of poorer people, he said.
Officials said the cut-off point had to be aligned with the higher-rate income tax threshold to ensure simplicity and avoid complex means testing.
But Mr Loughton indicated that it could be revised.
"If there are ways we can look at compensating measures for those genuinely in need that will be looked at in future budgets," he told Channel 4 News. "If the thresholds need to be adjusted there's plenty of time to look at that."
Seizing on his comments, shadow work and pensions secretary Yvette Cooper said: "The Government's unfair attack on child benefit is now unravelling.
"The Chancellor only announced means testing this morning, and already the Children's Minister has admitted that the thresholds need to be looked at again.
"George Osborne and David Cameron obviously don't understand what it means for families on middle incomes to lose thousands of pounds a year."
The Prime Minister will be grilled on the issue in a series of media interviews as he prepares for his own set-piece address to the Birmingham gathering on Wednesday.
