Submissions on the legislation close tomorrow and a select committee is due to report to Parliament in June.
"What this ban will do in the meantime is force more of the K2 product off the shelves and that is the best outcome we can have at this point with a product that is clearly bad for people,'' Mr Dunne said.
He said the industry and the outlets that sold the drugs had "no integrity whatsoever''.
"There is no goodwill and there is no decency in this industry, and that is why we are legislating. They prove day-in and day-out that they cannot be trusted.''
The two new substances being banned are BB-22 and 5F-AKB48, both of which have been found in K2 products.
From next Thursday it will be illegal to import, manufacture, sell or supply the substances, with penalties of up to eight years imprisonment.
"The Health Ministry considers that these particular substances pose a risk at least comparable to other already banned synthetic cannabis substances, therefore I have made the decision that it needs to be banned,'' Mr Dunne said.