The UK social security system's bottom line means-tested subsistence benefit, paid to households whose income falls below a set level (allowing for certain expenses and family situations). Formerly known as Supplementary Benefit ("Sup Ben" for short), Income Support is paid to top up various other benefits or earned income to the subsistence level. Additional income during any given week is deductible at a 1:1 rate from the benefit paid for that week, contributing to a poverty trap. Income support for those of the unemployed who do not receive any or enough National Insurance-based benefits has been lately rebranded as "Income Based Jobseeker's Allowance" but is payable at the same rates and under much the same restrictions.
At the time of writing, the basic levels of these benefits are £53.05 per week for single adults over 25 and £83.25 per week for a cohabiting couple both aged over 18.
Update: as of 14 February 2006 those rates had increased to £56.20 and £88.15 respectively.