Sajid Javid’s vow to “level up health” will fail unless the government reverses a decade of cuts to public health, an expert will warn on Monday.

The health secretary, Sajid Javid, has announced the creation of a new Office for Health Improvement and Disparities (OHID) and vowed it will have a “relentless focus” on health inequalities and “a driving mission to level up health”.

But the cross-government effort will flop if ministers do not prioritise the prevention of ill health and urgently restore funding to key public health services, Sir Michael Marmot will say in a speech at the Royal College of Nursing’s (RCN) annual congress.

“We need to adopt a health and social care system which prioritises not just the treatment of illness but how it can be prevented in the first place,” Marmot, the director of the UCL Institute for Health Equity, is expected to say.

“The pandemic has made it crystal clear over the last 18 months why public health and, more broadly, the social determinants of health, are so important,” he will add. “The health and social care agenda must be rebalanced more towards prevention.”

The OHID would lead a cross-government effort to address “the wider factors that contribute to people’s health outcomes”, Javid vowed last week. Health problems often depended on “your job, your housing, your environment, the education that you had and so much more”, he acknowledged.

Speaking at an event organised by the Centre for Social Justice at the Grange community centre in Blackpool, Javid insisted the OHID would have a “relentless focus” on health inequalities as part of the government’s “levelling up” agenda.

It will take over public health work from Public Health England. Javid said it would have “a driving mission to level up health and ensure everyone has a chance to live happy and healthy lives”.

But Marmot is expected to argue on Monday that the widening of health inequalities across the UK has at least partly been caused by a decade of dramatic cuts to public health spending by the government.

At the RCN congress, Marmot will tell delegates the underlying problem is “not that central government is telling local authorities not to act, it is that they have taken the funding away”.

Earlier this year a review he led into health inequalities found Covid-19 death rates were a quarter higher in Greater Manchester than in the rest of England. The more impoverished a local authority, the higher its mortality rate, his report showed.

Marmot said this “social gradient in mortality” was found across the country and reflected existing health and employment inequalities. In his speech he is expected to warn that “damaging” and deteriorating health inequalities in the UK can only be addressed with a greater focus on prevention.

In a swipe at Javid and Boris Johnson, Marmot will say that while he has seen impressive levels of engagement from politicians at local level and in some of the devolved nations, in particular Wales, the UK government has yet to follow suit.

“The prime minister spoke in July about how we didn’t know why people’s life expectancies in Glasgow and Blackpool were much lower than in Hertfordshire and Rutland. We do. It’s down to the fundamental, societal issues like poverty, poor housing and children not having enough food to eat,” he is expected to say.

The RCN is calling on the government to introduce a fully funded health inequalities strategy to address the social determinants of health, and to deliver a long-term, increased, sustainable funding settlement for public health that includes investment in public health nursing.

“Cuts to public health budgets must be reversed urgently,” said Pat Cullen, the RCN’s general secretary and chief executive. “The impact on patient care has been appalling in areas such as smoking cessation, obesity services and sexual health clinics.”

She added: “That the UK government has failed to grasp what is clear as day to the rest of the country is deeply disappointing.”