Prime Minister Gordon Brown has said he will look again at inheritance tax - after the Tories pledged to raise the threshold at which it is paid to £1m.
Mr Brown told Andrew Marr there could be a future debate
He questioned the funding behind the Tories' policy, but said the government was always "looking at these issues".
Neither party wanted to abolish it, but the question was about the rate it is charged at and the threshold, he said.
He told the BBC there could be a debate about the "fairest system" of inheritance tax "in future weeks".
During the Conservative Party conference, shadow chancellor George Osborne pledged to raise the threshold at which estates pay inheritance tax from £300,000 to £1m.
He said they would pay for the change with a £25,000 a-year charge on "non-domiciles" - people who live in the UK but do not pay tax on profits from income made abroad.
Labour criticised the policy - saying the levy would raise only a fraction of the £3.5bn needed and said it would create economic instability.
But the pledge attracted many positive newspaper headlines.
The Observer reported on Sunday that Mr Brown's decision not to call for an autumn general election came after private polls indicated the pledge had led to a drop in Labour's support in key marginal seats.
During the interview with Andrew Marr in which he ruled out an early election Mr Brown said it was easy for the Conservatives to pledge "£5bn of tax cuts" but said the question remained as to how you paid for them and how you maintained economic stability.