A new scheme to check up on disabled benefit claimants was the centre of a political row today.

Liberal Democrat Steve Webb told the party's annual conference in Bournemouth that the government was introducing the controversial new system "through the back door'' and said it would lead to people who were unfit for work losing out.

The new system - dubbed as "MOT Tests'' for claimants - will be piloted at Jobcentres in 17 areas of the UK next month.

It will require new Incapacity Benefit claimants to attend for work focussed interviews at job centres before receiving payments.

They will then have to undergo regular medical tests and repeat interviews every three years.

LibDem Work and Pensions spokesman Professor Webb said at a meeting with the Disability Rights Commission: "It caused outrage when the government announced these controversial changes without telling Parliament. Now we find the changes will be introduced by the back door without any Parliamentary scrutiny.

"The government is threatening to withhold benefit from disabled people who are unfit for work unless they come in to talk about job prospects. Given the many barriers to work already faced by disabled people and the discrimination that many suffer, forcing them to discuss jobs on pain of benefit is cruel and unnecessary.

"Disabled people who are able to work should be supported and not threatened. The benefit system itself is a barrier to disabled people taking part time work. IT relies too much on an "all-or-nothing'' notion of disability.

"The benefit system needs to be changed to allow people to combine part benefit with part-time work. This would do more good for disabled people than  threats by the government.''

But Work and Pensions Secretary Alistair Darling has rejected the allegations: "I announced the proposals in July, so they are not being introduced through the back door. I have just laid the regulations to allow a full Parliamentary debate about this next month.''

He said the move was about helping new claimants - not existing ones - into work. A spokesman for his department added:" We will not force people to come to Jobcentres who are not able to. They can be excused or we can visit them in their homes.

"Many disabled people will be happier and better off if we can find them work rather than write them off on benefit. Already many Incapacity Benefit claimants have to undergo regular medical checks. "