US President Barack Obama has sacked the boss of the Internal Revenue Service over a scandal sparked when officials unfairly targeted conservative groups, in the US.

Obama has promised a new system of checks and safeguards to avoid a repeat.

The President has dismissed Republican attempts to link him to the scandal at the agency.

He said evidence of abuses in the tax agency, revealed in a report by a government watchdog released earlier this week, were 'inexcusable'.

The scandal erupted when it emerged that officials studying tax exemption status applications singled out groups with words including Tea Party or Patriots in their titles, groups that would be expected to be fiercely opposed to Obama.

The White House says no-one in Obama's governing or political team had anything to do with the scandal.