But the chair of the Health Select Committee, Liz Craig, said National only gave the committee 24 hours notice, which was not enough time.
She said Prime Minister Jacinda Ardern has already signalled that the Government is looking into a review of Pharmac next year.
"What we wanted to do is take the time to understand where the Government is going with that and not commit to it straight up."
But Reti said waiting for next year was not good enough.
"This is a slap in the face, not only to the many thousands of New Zealanders who have been calling for the same thing, but particularly to those who marched with Crohn's and Colitis NZ, calling on Pharmac to fund a medication to help those suffering with the diseases."
The new Health Select Committee met for the first time this morning behind closed doors. Reti is not a voting member of that committee but acts as an observer and contributes to the meetings.
The committee is made up of mostly Labour MPs. Liz Craig – elected in 2017 – is its chair.
This morning's motion for the committee to initiate an inquiry into unfunded medicines in New Zealand, as well as the drug-buying agency Pharmac, was moved by National's Matt Doocey.
But the motion was only supported by National's three MPs on the committee, as well as the sole Act MP. The Greens MP on the committee voted against it, as did the five Labour MPs.
The makeup of select committees is an important part of Parliament's democratic process.
After a bill's first reading, it goes to one of a number of committees to be scrutinised.
The MPs on those committees also hear submissions from members of the public, and vote on things such as initiating inquiries.
Some relatively new MPs have been given important roles, particularly the class of 2017.
Hutt South MP Ginny Anderson has been made the chair of the Justice Select Committee, and her deputy is newly elected Vanushi Walters.
Labour's Tāmati Coffey will head the Māori Affairs committee with Arena Williams as his deputy, and Jamie Strange is now in charge of the Economic Development, Science and Innovation Committee.
Duncan Webb – Labour MP for Christchurch Central – has been announced as the chair of the all-important Finance and Expenditure Committee.
Although Labour holds the most committee leadership posts, National has managed to snag a couple.
Jacqui Dean will head the newly created Petitions Committee, Barbara Kuriger is in charge of the Governance and Administration Committee, and Chris Penk will chair the Regulations Review Committee.