It looks as if there are two types of ESA, one taxable and the other not, according to part of the DirectGov website:
http://www.direct.gov...llorinjured/DG_171896
In case the link doesn't work, it says:
" Income Tax
Income-related Employment and Support Allowance is not taxable.
It's important to note that contribution-based Employment and Support Allowance is taxable, so you may have to pay tax. How much tax, if any, you have to pay depends on whether you receive any other income, for example, an occupational pension.
Depending on your circumstances, you may get a new tax code."
Good luck sorting it out.