The Government originally proposed restricting all RTDs to no more than 5 per cent alcohol content.
But this was later amended to 6 per cent, with higher-strength drinks permitted in restaurants and bars.
Alcohol industry giants have put pressure on the minister to scrap rules altogether for ready-to-drink beverages, arguing that they unfairly targeted one part of the industry and threatened to breach international trade rules.
Mrs Collins dismissed the suggestion that changing the rules on RTDs would lead to complaints to the World Trade Organisation (WTO).
"The WTO threat is just nonsense... because we have never proposed preventing the importation or sale of particular products.
"But what we have said is that we could look at ... where they are sold in New Zealand and that is not something that is an issue for the WTO."
In the Law Commission report the reforms were based on, the commission said the most common drinkers of RTDs were 14 to 24-year-olds, in particular women.
The bill was originally set to return to Parliament for its third reading this month. Mrs Collins said it was now likely to be debated after the next Parliamentary recess.
MPs will have to decide whether to keep the minimum age at 18, raise it to 20 for off-licenses, or raise it to 20 in both off-licenses and on-license premises.
Mrs Collins said working out which order to hold the vote so that no option was unfairly biased was highly complex.
"It is important that it doesn't turn into a complete mess, as previous alcohol reform bills have."