A husband who battered his ex-wife with a nail-spiked bat because she 'cheated' has been spared jail by judges who quoted the Bible to justify the lenient sentence.

Women's rights groups have called for protests after the court in Porto, Portugal said it had 'some understanding' for the attacker because adultery is 'a very serious offense against a man's honor and dignity.'

The man was given a 15-month suspended sentence and a fine of 1,750 euros for using a bat studded with nails to assault the woman in the street in 2015, leaving her covered in cuts and bruises.

The prosecutor had argued the sentence was too lenient and asked an appeals court for prison time of 3 years and 6 months. But the appeal judges on October 11 rejected his request.

A husband who battered his ex-wife with a nail-spiked bat because she 'cheated' has been spared jail by judges in Porto (pictured), Portugal, who quoted the Bible to justify the lenient sentence

In their written ruling, the judges said adultery is 'a very serious offense against a man's honor and dignity.'

They also noted the Bible says an adulterous woman should be punished by death and cited a 1886 Portuguese law that gave only symbolic sentences to men who killed their wives for suspected adultery.

The judges at the appeals court in Porto, Portugal's second-largest city, wrote that they were making reference to the Bible and an old law 'to stress that a woman's adultery amounts to conduct which society has always condemned and condemned very strongly.'

The written ruling became public this week and sparked outrage on Portuguese social media, with numerous rights groups speaking out.

The UMAR Women's Union for Alternative and Response called the verdict in Portugal's second-largest city 'revolting' and said it perpetuated 'the ideology of victim-blaming'.

'Evoking the Bible does not combine with the rule of law in our country and discredits the judicial norms,' UMAR said in a statement.

In their written ruling, the judges said adultery is 'a very serious offense against a man's honor and dignity'. File picture shows a Portuguese police officer

In the 2015 attack, one of the men assaulted and held the victim while the other attacked her with a nail-spiked club. Her injuries were not life-threatening.

Both were convicted and sentenced to pay large fines in addition to suspended time in prison of about a year each.

UMAR and the feminist movement Por Todas Nos (For all of Us Women) called a protest rally in downtown Lisbon for Friday. Protests were also called in Porto under the slogan 'Male chauvinism is not justice, but crime'.

Ultra-orthodox patriarchy - one of the cornerstones of the fascist dictatorship of Antonio Salazar up until the 1974 revolution - still survives in parts of Portugal.

Portugal's Superior Magistrates Council, an oversight body, said it had taken note of the 'vivid criticism from broad sections of public opinion.'

However, it said courts are independent and it could not intervene, even when faced with 'archaic, inappropriate or unfortunate' comments by judges.

The woman could appeal to Portugal's higher courts.