LONDON (AFP) - Two of Britain's most dangerous sex offenders will have to spend at least 40 years in prison, judges ruled on Friday (Dec 11), after a government appeal that their sentences were too soft.

Britain's attorney-general had sought to ensure that Reynhard Sinaga and Joseph McCann spend the rest of their lives behind bars because of the extent and nature of their crimes.

But five appeal court judges, including the head of the judiciary of England and Wales, Lord Chief Justice Ian Burnett, refused to impose whole-life terms.

"The offending in the cases of McCann and Sinaga, very serious though it is, does not, in our judgment, call for either to receive a whole life tariff," Judge Burnett said in the ruling.

The judges said both men's crimes were among the most serious offences of rape to have been tried in the courts of England and Wales.

Neither had shown any remorse, they added, as they increased the minimum time they must spend in prison from 30 to 40 years.

Sinaga, an Indonesian national, was convicted of 159 offences, including 136 rapes and eight attempted rapes, at four separate trials which began in June 2018 and ended last December.

The 36-year-old lured unsuspecting men to his flat in Manchester, north-west England, drugged, then assaulted them, and captured the attacks on camera.

Police believe he may have attacked as many as 195 men. The sentencing judge called him "an evil serial sexual predator" and a "monster".

McCann, 34, was jailed in January after a cocaine-and-vodka-fuelled rampage against 11 people aged between 11 and 71 in and around London, and north-west England.

The judge who sentenced him for 37 charges of rape, sexual assault, kidnap and false imprisonment branded him a "coward, a violent bully and a paedophile".

The attorney-general - the government's most senior law officer - has powers to appeal against certain sentences by judges in England and Wales if they appear to be "unduly lenient".

Whole-life orders are usually restricted to the most serious cases of murder.

At the appeal in October, Solicitor-General Michael Ellis said both men's crimes were "some of the worst and most violent that this country has ever witnessed".

On Friday, he said he hoped the judges' ruling "brings some solace to the victims of these despicable crimes".