Benefit claimants could find themselves "trapped in poverty" when a new single welfare payment is introduced next year, it is being claimed.

While the Universal Credit was sound "in principle", the Joseph Rowntree Foundation said its implementation could leave some people worse off.

It warned any financial gains people might make in part-time jobs may be wiped out if they found full-time work.

Officials said anyone struggling would get the help they needed.

In the biggest shake-up of the welfare system in generations, the single consolidated payment will replace a host of existing working age benefits for new claimants from October 2013.

Ministers say the Universal Credit - to replace income-based Jobseeker's Allowance, income-related Employment and Support Allowance, Income Support, Child Tax Credits, Working Tax Credits and Housing Benefit - will increase work incentives and reduce poverty among those on low incomes by ensuring people keep more of their income in employment and benefits are withdrawn more gradually.

But analysis of the new system for the Joseph Rowntree Foundation, by the University of Portsmouth and the Centre for Social and Economic Inclusion, has raised serious concerns about its administration and potential outcomes.