Sir Keir used an article in the Mail on Sunday today to signal a new focus on domestic politics, after the extraordinary Budget tax raid and a backlash over his globetrotting fueled a slump in Labour’s poll ratings.

He said that the reforms announced this week will pave the way for ‘the biggest overhaul of employment support in memory’.

He wrote: ‘Make no mistake, we will get to grips with the bulging benefits bill blighting our society.’

‘Don’t get me wrong – we will crack down hard on anyone who tries to game the system, to tackle fraud so we can take cash straight from the banks of fraudsters.

‘There will be a zero-tolerance approach to these criminals. My pledge to Mail on Sunday readers is this: I will grip this problem once and for all.’

Labour’s plans include giving the NHS a role in getting people back to work, such as employing tens of thousands of people who are economically inactive for health reasons in non-clinical roles.

Ms Kendall’s White Paper is also expected to include the placement of work coaches in mental health clinics.

She said that she believed ‘many millions’ of disabled people and those with long-term health problems want to work, and ‘we need to break down the barriers to that happening’.

‘Look, don’t get me wrong, the benefits system can incentivise or disincentivise work. But there are many other things we need to do to get people back into work,’ she said.

‘I do not want an ever-increasing benefits bill spent on the cost of failure, people trapped out of work, terrible for their life chances and paid for by the taxpayer. We need big reforms to make that happen.’

Ms Kendall said young people have a ‘responsibility’ to take up opportunities for work and will face sanctions if they do not do so.

‘We will transform those opportunities for young people, we will put in place a youth guarantee so everyone has the chance to be earning or learning,’ she told the BBC’s Sunday with Laura Kuenssberg.

‘But in return for those new opportunities, young people will have a responsibility to take them up.

‘Let me tell you why, because if you lack basic skills in today’s world, that is brutal. If you are out of work when you’re young, that can have lifelong consequences in terms of your future job prospects and earnings potential.

‘So, we, the Government, will face up to our responsibility, unlike the last government, of having that guarantee in place.’

She said young people she had spoken to said it was ‘better for their mental health’ to be in work.

Labour has said it will stick to a commitment under the former Tory administration to reduce the welfare bill by £3billion over five years.

Under the previous government, welfare eligibility would have been tightened so around 400,000 more people signed off long-term would be assessed as needing to prepare for work by 2028-29 to deliver the savings.

But Ms Kendall suggested the proposals – which could have cut handouts by around £400 a month – would be changed.

She told the BBC’s Sunday With Laura Kuenssberg: ‘We will deliver those savings, we will bring forward our own reforms. You will hear more about this when we launch our white paper on Tuesday.’

Asked whether those people will be able to keep their benefits, she said: ‘I’m saying we will bring forward our own reforms. You wouldn’t expect me to announce this on your programme. But my objective is that disabled people should have the same chances and rights to work as everybody else.’

The number of people claiming incapacity benefits is forecast to rise from 3.2 million last year to 4.2 million in 2029 – costing Britain £35.5 billion by the end of the decade.

In 2019, there were 2.5 million people claiming these benefits, at a cost of £17 billion.

In his MoS article, Sir Keir tried to reassure the Labour Left that he is not aping Tory policies by saying that the reforms will not ‘sow division’ by describing people on benefits as ‘shirkers’, but would instead ‘treat people with dignity and respect’.

The proportion of young people not in employment, education or training (NEET) has been rising

He singled out shadow chancellor Mel Stride, who was Work and Pensions Secretary in Rishi Sunak’s Government, for supposedly having ‘picked fights instead of governing’ and using ‘meaningless rhetoric to grab headlines’.

But a Tory Party spokesman said: ‘Labour’s hollow promises on welfare reform will fool no one. When the last Conservative government introduced messages to tackle the growing benefits bill, Labour opposed them every step of the way.

‘At the Budget, instead of following in our footsteps and taking difficult decisions on welfare to fund public services, Rachel Reeves instead reached straight for the tax lever.

‘This new government has no clue what is needed to get people off benefits and back into work.’

The Institute for Fiscal Studies has said that it is not clear why the costs of benefits have increased so much in the UK since Covid because the trend has not been seen in other countries.