The government's programme of disability benefit reforms have been introduced across the UK.
Disability Living Allowance (DLA) has been replaced for new claimants aged 16 to 64 with Personal Independence Payment (PIP.)
The Department of Work and Pensions (DWP) has started taking new claims for PIP in parts of the North of England in April 2013. They have now extended this to cover all parts of Great Britain from June 2013.
Esther McVey, minister for disabled people said: "DLA is an outdated benefit introduced over 20 years ago and was very much a product of its time.
"PIP has been designed to better reflect today's understanding of disability, particularly to update our thinking on mental health and fluctuating conditions."
Under new assessment criteria, claimants will be asked to attend regular reviews and face-to-face assessments with an independent health professional. The health professional will ask questions about the claimant's health condition or disability and how this affects their daily life.
It has also been confirmed that existing DLA claimants will not be re-assessed until 2015 or later, after the DWP has considered the findings of the first independent review in 2014.
However, there have been concerns about the impact on the reforms on current and future claimants.
The government has spent over £13bn a year on DLA. In ten years, the number of people claiming DLA has risen by almost 32% (from 2.4 million to 3.3 million). However, figures from the DWP estimate around 450,000 claimants will no longer be able to claim disability benefits by 2018.
Richard Hawkes, chief executive of disability charity Scope, described the government's assessment for PIP as "deeply flawed."
"DLA needed reforming and could be better targeted. But disabled people believe this reform is just an excuse to save money. It doesn't help that the minister is able to predict exactly how many disabled people will receive support before they have even been tested.
"For months now we have been saying the government's assessment for the new PIP is deeply flawed. It doesn't take into account all the barriers that disabled people face in daily life. This means the support won't be targeted to those that really need it. It looks set to repeat the mistakes of the Work Capability Assessment."
