National Party Leader John Key says the Government should immediately signal to Pharmac that it will free up funding for Herceptin if it's required.

"What's really worrying, is the nagging feeling that this has been a financial decision not to fund Herceptin, rather than a decision founded in the best interests of Kiwi women.

"To deal with that suspicion, Helen Clark should tell Pharmac they'll get extra resources to provide Herceptin if required."

Mr Key is commenting in the wake of the latest Lancet report that suggests very significant benefits from the use of Herceptin for early stage breast cancer.

"This is the research that New Zealand authorities have said they've been waiting for.

"Pharmac's budgets are very tight but Labour is sitting on an $11 billion surplus which it won't spend because of an inflationary environment of its own making.

"What we're talking about is an investment of $20-$25 million in the health of New Zealand women. Labour must sort out its priorities."

Mr Key is confident Herceptin will eventually be funded but he is urging Helen Clark to speed up the process by signalling that funds are available if required.

"A timely decision now could mean the difference between life and death for some."