The law, introduced earlier this month, made adultery and gay sex punishable by death by stoning.
The country also revealed thieves faced amputation, and people who wore clothes that were not made for their gender would be whipped.
The southeast Asian country has defended the law in a letter written to the European Parliament.
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The letter asked for "tolerance, respect and understanding" of their stance, and said that the “criminalisation of adultery and sodomy” was designed to safeguard the “sanctity of family lineage and marriage to individual Muslims, particularly women.”
It also said the crimes that were punishable by stoning to death required a high evidentiary threshold, and there must be two or four men of "high moral standing and piety as witnesses".
Udo Bullmann, the German MEP who leads the Socialists, Parliament’s second biggest political grouping, accused Brunei of “trying to defend the indefensible.”
He added, “We will never condone the death penalty for LGBT and will do all we can to sanction it heavily.”
“We will never condone the death penalty for LGBT and will do all we can to sanction it heavily” Udo Bullmann, S&D leader
Further comment came from S&D group spokesperson on human rights, Soraya Post, who told this website, “The new Sharia penal code in Brunei is cruel, degrading and inhumane. It targets already vulnerable groups in society: children, women and LGBTI people and deprives them of their human rights.”
“According to the new laws, children as young as seven years old can be punished by flogging and whipping. Consensual same-sex acts and abortion can be punished with death by stoning or by flogging and whipping.”
"The punishments are ancient and evil, as is the mind-set of the monarchy in Brunei. In civilized societies where human rights are respected, it is not a crime to be gay, lesbian or bisexual or to have an abortion.
“I demand an immediate end to this Sharia penal code. Otherwise, the EU will have no choice but to impose tough sanctions on Brunei’s government officials and Sultan. They should face travel bans and financial sanctions including seizure of their assets,” Post added.
Parliament last week also condemned Brunei’s new penal code.
The resolution adopted by overwhelming majority calls for consideration of sanctions such as asset freezing and visa bans in the event of implementation of the penal code.
“The new Sharia penal code in Brunei is cruel, degrading and inhumane. It targets already vulnerable groups in society: children, women and LGBTI people and deprives them of their human rights” Soraya Post MEP
Parliament has also called for the possible freezing of valuable assets, including a number of high-end hotels owned by Brunei globally.
Celebrities such as George Clooney and Elton John have also called for people to boycott Brunei-owned hotels earlier this month, with Elton John saying he has "long refused" to stay at the hotels.
Sultan Hassanal Bolkiah, who is also Brunei’s Prime Minister, said the anti-gay law was a "great achievement".
Brunei has banned homosexuality since 1964, but has implemented harsher punishments since embracing a radical interpretation of Islam.