evidence: NORTHERN Ireland's cost to the British Exchequer rose to £10.3 billion last year - and is likely to increase even further. [...] The Office for National Statistics (ONS), in its country and regional public sector finances report for the financial year to April last year, shows that total public expenditure relating to Northern Ireland was about £30 billion, while the total value of tax revenue relating to the region was around £20 billion. [...] "This position is an outcome of a combination of relatively high levels of public spending in Northern Ireland alongside relatively low levels of tax revenues generated.