Sir Keir Starmer will set out a “plan for change” with milestones set in key policy areas to achieve the targets laid out in Labour’s manifesto, Downing Street has said.

The Prime Minister will this week kick off what he has called the “next phase” of Government, as he announces the markers for his “missions” that Number 10 say will allow the public to hold Sir Keir and his team to account on their promises and will be reached by the end of the Parliament.

The milestones will run alongside public sector reform, Downing Street said.

Given the unprecedented challenges we have inherited we will not achieve this by simply doing more of the same

This will include a focus on reforming Whitehall, spearheaded by the as-yet-unannounced new chief civil servant the Cabinet Secretary and Cabinet ministers, so it is geared towards the delivery of Labour’s missions, according to Number 10.

The same focus will also influence decisions for next year’s spending review, it has been suggested.

Writing in The Sun on Sunday, the Prime Minister compared “focusing the machinery of government” to “turning an oil tanker” and said that “acceptance of managed decline” has “seeped into parts of Whitehall”.

“The British people aren’t fools. They know a ruthless focus on priorities is essential,” he wrote.

The Sunday Times reported that one of the milestones would focus on early education, with the aim to raise the number of children who are ready for school, educationally and socially. Cabinet Office minister Pat McFadden said that “it’s estimated that more than a million school days worth of teacher time each year is spent dealing with” children who are not prepared for school.

Labour’s missions, as laid out in their July election manifesto, focus on economic growth, energy security and cleaner energy, the NHS, childcare and education systems, as well as crime and criminal justice.

Ahead of revealing the details, Sir Keir said in a statement: “This plan for change is the most ambitious yet honest programme for government in a generation.

“Mission-led government does not mean picking milestones because they are easy or will happen anyway – it means relentlessly driving real improvements in the lives of working people.

“We are already fixing the foundations and have kicked-started our first steps for change, stabilising the economy, setting up a new Border Security Command, and investing £22 billion in an NHS that is fit for the future.

“Our plan for change is the next phase of delivering this Government’s mission.

“Some may oppose what we are doing and no doubt there will be obstacles along the way, but this Government was elected on mandate of change and our plan reflects the priorities of working people.

“Given the unprecedented challenges we have inherited we will not achieve this by simply doing more of the same, which is why investment comes alongside a programme of innovation and reform.”

The so-called “missions” outlined in Labour’s election manifesto focused on five key policy areas: kickstart economic growth; make Britain a clean energy superpower; take back our streets; break down barriers to opportunity; and build an NHS fit for the future.

The announcement comes after a first five months in office that has seen anger over Budget proposals and reports of tension in Number 10.

Polling for The Observer newspaper by Opinium indicates that more than half of the public disapprove of the Prime Minister’s performance.

According to the survey of approximately 2,000 adults, 54% of people disapprove of his performance, compared with 22% who approve, leaving him with a net rating of -32%.

It comes as the Sunday Telegraph reported that Labour’s governing body had agreed to plans that could impact mayors.