The UK government’s promise to reverse rising obesity rates in the next decade is “doomed to fail” without a major rethink and a new plan led directly by the prime minister, a cross-party committee of MPs has concluded.

The health and social care select committee said in a report that there are no signs the so-called “moonshot ambition on obesity”, set out in the 10-year health plan for England, will achieve anything significant.

More than a year after the promise to “end the obesity epidemic” within a decade was made, even the most basic questions – such as how progress will be measured and how a cross-departmental plan would work – remain unanswered, the MPs said.

The report said: “While the ambition to ‘end the obesity epidemic’ is a laudable one, we currently have no faith in the government’s commitment to this aim or ability to achieve it and predict that, unless they urgently reassess their approach, they are doomed to fail.

“The government will fail to tackle a challenge of this scale unless action is led from the top and delivery of the moonshot is made a clear, personal priority of the prime minister.”

It called for the creation of a dedicated cabinet committee on the obesity plan, chaired by the prime minister, to drive action and “to send a message that this government takes obesity seriously”.

According to the most recent official statistics, 30% of adults in England are living with obesity, with 66% either overweight or living with obesity. Close to a third of children are now estimated to be overweight or living with obesity. Obesity rates for adults and children have increased significantly since the 1990s and, while the trends have levelled off, there are no signs of a fall.

One of the major failings of the current strategy, the report said, is a lack of proper distinction between efforts to prevent future obesity, for example by cracking down on unhealthy foods, and those to support and treat people who already have obesity.

“Conflating these two things is in part responsible for the muddled thinking and lack of progress from successive governments to date,” the MPs said.

Any effective plan must be based on a clear definition of what the ambition to reduce obesity rates means in practical terms, along with interim progress markers that would allow MPs to hold ministers to account, they said.

The MPs also called for a “joined-up, cross-government action plan”, taking in the departments responsible, their planned actions and how these will be funded, covering prevention and treatment for adults and children.

Ministers should come to parliament within the next three months to set out the plan, the report said.

Leadership from No 10 was vital, said Layla Moran, the Liberal Democrat MP who chairs the committee. She added an effective plan “will mean standing up to the food industry on numerous points – regulating the constant presence of adverts and promotions for unhealthy food and drink that wallpaper our lives, simpler labelling on products, targets for supermarkets to sell more healthy foods and restricting fast food outside schools”.

She said: “This issue transcends government departments, and experience tells us that if the prime minister isn’t calling the shots on such a huge societal issue, the loose ends won’t join up and the moonshot will crash land.

“We urge him to take up this ambition and be the driver of change. In turn, the NHS, public health and the economy will reap the long-term benefits.”

A Department of Health and Social Care spokesperson said: “Obesity is one of the biggest challenges facing our health service, and this government is taking bold action to help drive the shift from sickness to prevention and give every child the best start in life.

“We have already restricted junk food advertising on television before 9pm and online, banned volume-price promotions on less healthy food and drink products, and given councils stronger powers to block new hot food takeaways near schools.

“Alongside our focus on prevention, we are supporting those already living with obesity by expanding access to weight management support, including NHS weight-loss drugs for those with the greatest clinical need.”