Speaking exclusively to UTV, Mr Larkin, who is the Executive's chief legal adviser, said mandatory sentencing was tried before and found wanting.

His comments come after a Spanish man was jailed for four years after admitting throwing a breeze block at a policewoman during four nights of sectarian rioting in Ardoyne last July.

The policewoman was seriously hurt when the missile was thrown on her head from the Ardoyne shopfront roof.

Rodger Jorro Costa, who is 29 and originally from Barcelona but with an address in Ulsterville Avenue in Belfast, had originally been charged with trying to murder the officer.

He later pleaded guilty to the lesser charges of attempted grievous bodily harm with intent and rioting arising from the incident.

On Monday Recorder of Belfast Judge Tom Burgess said he was lucky not to be facing more serious charges as he could easily have caused fatal injuries to the officer.

The sentencing has prompted calls from the Police Federation for a tougher crackdown on rioters.

The body representing rank and file PSNI officers says that anyone detected and charged with riotous behaviour should face immediate imprisonment.

However the government's chief law officer said the use of mandatory sentences during the Troubles was not "an entirely a happy one".

Where you introduce rigidity in one part of the system, it often produces bulges and undue flexibility elsewhere.

Attorney General John Larkin QC

North Antrim DUP MP Ian Paisley has written to the Attorney General to ask for Costa's sentence to be reviewed.

"I think the public want to see longer, stiffer sentences," he told UTV.

"The Public Prosecutor too could come out and make a public statement and explain their actions as to why an attempted murder charge was not brought in the case of Mr Costa and why more serious charges were not preferred on other of these criminals.

"We need to see tougher sentencing and we also need to see the strongest possible charges brought to ensure that there is proper deterrent out there for the public."

In a statement, a PPS spokesperson denied that Costa's charge was reduced as a result of a plea bargain.

"No bargain was entered into. Any suggestion that the PPS has gone for a lesser charge is misconceived.

"The accused was prosecuted for riot and attempting to cause grievous bodily harm with intent which carry the same potential maximum penalty of up to life imprisonment as attempted murder.

"The fact remains that this reprehensible incident was properly prosecuted and all persons brought before the courts arising out of the rioting have been convicted of serious offences."

John Larkin was speaking to UTV during the course of a wide-ranging interview on criminal justice.

He also dismissed claims that prosecution barristers in Northern Ireland are engaged in plea bargaining, a process whereby defendants are given the opportunity to plead guilty, usually to a lesser charge or to the original criminal charge with a recommendation of a lighter sentence.

Several other men have also been sentenced over the disturbances at the Belfast interface.