The Tories sought more tax pledges from Labour yesterday as national insurance and child benefit once again became the subject of election speculation.

Having been pressed at Labour's morning press conference to rule out removing the ceiling on national insurance contributions, Tony Blair refused to give a specific promise.

"What we have said is clear. We are not sitting here writing a budget but we have got no intention of clobbering higher earners."

Later the Tory's social security spokesman David Willetts claimed that Gordon Brown planned to fill a "black hole" in his spending plans by taxing or means-testing child benefit.

Gordon Brown dismissed the claim as "a typical Tory tax smear" and said that families could be "absolutely reassured" that child benefit would not be taxed and would "rise in line with prices" under a Labour government.