Labour leader David Cunliffe "can't have it both ways" on his proposed capital gains tax, National's finance spokesman says.

Mr Cunliffe was put under pressure about the policy during a leaders' debate with John Key last night when he was asked whether family homes in trusts would be exempt.

He was briefly rattled and was unable to answer the question during the debate, but tried to clarify the situation afterwards stating that they would be.

National's finance spokesman Bill English disagrees, however.

"Nowhere in Labour's capital gains tax policy does it exclude family homes owned by trusts," he says.

"In fact, Labour actually says: 'We will ensure trusts are not used as a means of avoiding a CGT'. David Cunliffe cannot have it both ways."

Mr English says the tax has been Labour policy for three years, and Mr Cunliffe's confusion over the details will leave New Zealanders uncertain.

During the debate Mr Key alleged that 300,000 family homes in trusts would come under Labour's capital gains tax policy, a figure given to him by an unnamed tax expert.

After the debate, Mr Cunliffe stressed that Mr Key was wrong and that family homes in trusts were exempt from the capital gains tax policy.


"I've learned to check my facts and John Key got it wrong, a family home does not incur Capital Gains Tax whether its owned by a trust or not. John Key got that wrong."

The leaders went on to debate child poverty, spending, housing, state housing and tax.

Dirty politics of course couldn't be kept out of the debate, with Mr Key for the first time publicly condemning Cameron Slater, the Whaleoil blogger at the centre of the saga.