Asked if the intention to write a national policy indicated the possibility of mandatory fluoridation, he said, "I'm not going to pre-judge that."
Greens health spokeswoman Sue Kedgley said her party supported "alternatives to mass-medication of water" - dental hygiene and reducing high-sugar foods and drinks - and local decision-making on fluoridation.
"It shouldn't be imposed on all New Zealanders through some national standard."
Mr Robertson said health funding had not kept up with inflation and population growth and ageing under National.
Labour would stop that, he said, but he could not put a dollar figure on it until in government.
Health Minister Tony Ryall said: "Is that it? After three years of criticising everything we've done, all Labour can come up with is a copy of our free under-6s after-hours policy and a promise to borrow more money."
Keeping NZ well
Labour's health policy promises:
* An inquiry into fluoridation of drinking water.
*Free primary care, 24/7, for children under 6.
*An end to what it says is National's "under-funding" of health.
*Tighter controls on alcohol, including minimum prices, advertising restrictions and a lower drink-driving tolerance.
*The end of "post-code" access to elective surgery.