Plans for rolling out weight-loss drug Mounjaro are "unambitious" and will reach a "woefully small number of people", according to MPs.
They say just 6% of those eligible will get - or currently receive - the drug in its first three years on the NHS, with millions buying it privately instead.
The warning comes from the Commons' health committee, which wants obesity treated as a long-term and managed condition like diabetes.
Mounjaro (tirzepatide) is one of the best known GLP-1 drugs, along with Wegovy and Ozempic, and is taken as a weekly injection.
It works by suppressing appetite and making a person feel fuller for longer.
MPs say its rollout needs to be ramped up dramatically as a "two-tier system" has formed between those who can afford to pay privately and those who can't.
"The government must urgently reassess the pace of rollout of Mounjaro," the committee urged.
"This should include making better use of the capacity of digital providers.
"As a first step, the department should hold a summit on GLP-1 access with a range of providers and healthcare professionals to open a dialogue on how best to improve the rollout."
The National Institute for Health and Care Excellence (Nice) recommended Mounjaro to treat obesity in June 2024.
Wegovy (semaglutide) has also been approved by the NHS.
The NHS estimated 2.8 million people would be eligible for Mounjaro, at a cost of £15.2bn over five years, if all signed on for the drug in its first year of availability.
Nice agreed to NHS England's request to introduce it gradually instead, and it's only being rolled out to 220,000 over three years.
The MPs' report calls for a new framework to "include ambitious targets for the proportion of a local population that should be able to access GLP-1s".
It says around 2.4 million packs of GLP-1 drugs are prescribed each month in the UK but the vast majority are being bought privately.
Prices for a month's supply of Mounjaro range from about £150 for the smallest dose to about £350 for the highest.
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"Access to GLP-1 medication appears increasingly to be determined by ability to pay rather than clinical need," the MPs warn.
"Given that obesity already follows stark lines of deprivation and inequality, failing to provide equitable access will entrench and widen those disparities, letting down the patients who need support most."
An NHS spokesperson said it was "testing new ways to accelerate access, including new routes for starting these medicine".
It said "a wide range of other support" for obesity was also available, "which has already helped tens of thousands of people achieve a healthier weight".
(c) Sky News 2026: Mounjaro rollout on NHS needs 'urgent' boost, say MPs
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