Liverpool will be hit 'disproportionally' hard by welfare reform, and charities fear disabled people will be most affected.
The Disability Living Allowance (DLA) will be replaced by Personal Independence Payment (PIP) for people aged 16 to 64 from 8 April.
The biggest shake-up of the welfare system since its birth is starting in Oldham, Tameside, Warrington and Wigan.
The minister for disabled people and Tory MP for Wirral West, Esther McVey, said changes to the benefit system are about "understanding disability in the 21st century" and adapting a system which will work better in the future.
The MP said the new scheme is not aimed at saving money.
A new benefit which replaces the Disability Living Allowance for people with a health condition or disability aged 16 to 64 is introduced in the North West today.
The Personal Independence Payment (PIP) scheme will first be introduced for new claims in Merseyside, North West England, Cumbria, Cheshire and north-east England.
It will be rolled out nationally for all new claims from June 2013.
- The personal independence payment scheme is being introduced for people with a health condition or disability aged 16 to 64.
- From today, it will be introduced for new claims in Merseyside, North West England, Cumbria, Cheshire and North East England. It will be rolled out nationally from June.
- Currently, there are no current plans to replace Disability Living Allowance (DLA) for children under 16 and people aged 65 and over who are already receiving it.
- Some people may require an assessment to work out the level of help needed.
- Most people currently getting DLA will not by affected by the change until 2015, according to the government.
Our political reporter Daniel Hewitt reports from Warrington, one of four 'pathfinder' towns in the North West, trialling the government's answer to Britain's bloated benefit system.
The government has faced fierce protest over the decision to charge people in social housing for their spare bedrooms.
Today, a cross party report said the reform could end up costing more money, increase homelessness and badly affect the poorest in society.
Work and Pensions Secretary Iain Duncan Smith has announced that foster carers and army personnel who receive housing benefit will be exempt from the so-called "bedroom tax".
In a Written Ministerial Statement, he wrote: "People who are approved foster carers will be allowed an additional room, whether or not a child has been placed with them or they are between placements, so long as they have fostered a child, or become an approved foster carer in the last 12 months.
"Adult children who are in the Armed Forces but who continue to live with parents will be treated as continuing to live at home, even when deployed on operations."