UK prime minister Boris Johnson has appointed a former senior Treasury aide to be his chief adviser on “levelling up” to tackle concerns in Whitehall that few know what the slogan is supposed to mean.

Neil O’Brien, the Conservative MP for Harborough who also served as a special adviser to former chancellor George Osborne and ex-prime minister Theresa May, has been asked by Johnson to oversee the programme that many recently elected Tories believe is critical to their re-election.

Following the 2019 election, when the Conservatives won scores of seats in northern England and the Midlands for the first time in the so-called “red wall” of traditional Labour strongholds, Johnson pledged to “level up” the country to tackle regional inequalities.

The prime minister pledged to repay the trust of first-time Conservative voters by seeking to rebalance opportunities across the country. “Those people want change. We cannot, must not, must not, let them down,” he said at the time.

But since 2019, critics say the government has struggled to explain the specifics of the programme, what policies it will include and how its success will be measured.

Initiatives such as the government’s levelling-up fund in the Budget led to ministers facing accusations of finding ways to channel funds to Conservative constituencies rather than address areas of economic weakness.

One senior Cabinet Office official said there was “a widespread cluelessness” within the government about what levelling up meant. This confusion has spread into Downing Street. With the departure of Dominic Cummings, Johnson’s former chief adviser, it has become a running joke among Number 10 staff that “it’s a slogan without a purpose”.

A senior Treasury official said that across government there was a range of views on what the policy should look like, including a focus on regional productivity differences, worries about smaller towns and opportunities for younger people in less prosperous areas. No one could decide, the official said.

The appointment of O’Brien, who is seen in the Conservative parliamentary party as one of the most policy-orientated MPs, is an effort to add clarity and substance to the slogan. One red wall Tory MP said: “If anyone can make sense of this, it’s Neil. It’s a great appointment.”

Some government insiders think there is no need to have a set view. One said there would be four parts to the levelling-up agenda: a regional economic policy, spreading opportunity across the country, improving the outputs and outcomes from public services, and non-economic outcomes of improving “quality of life” and “pride in place”.

The danger of the all-encompassing view, however, is that the policy lacks focus, making it hard to demonstrate results have been achieved.

O’Brien will work across Downing Street and the Cabinet Office on levelling up. He will also work closely with the new Number 10 delivery unit, a team that oversaw the implementation of government policy under former Labour prime minister Tony Blair.

Johnson has had in-depth conversations recently with Sir Michael Barber, who created the unit, about ensuring Whitehall can deliver on the Tories’ manifesto pledges.

Sir Michael is also undertaking a review of the effectiveness of the civil service to ensure Whitehall is in “the very best shape to deliver” on government policy.

“Sir Michael is making lots of very strong recommendations. He’s been given a free moving remit to help the PM to deliver on manifesto,” one Whitehall official said. “He will be shaking every tree in Whitehall”.