Kuwait cannot claim to be a beacon of freedom in the Gulf if it sends people to jail for remarks deemed offensive towards the ruling emir, and it must amend its penal code, Human Rights Watch said on Thursday.
Since October, prosecutors have charged nearly 25 people with offending Emir Sheikh Sabah al-Ahmad al-Sabah, sentencing at least six of them to jail terms, the US-based body said.
"Sending politicians to prison for criticizing the ruler is at odds with official claims that Kuwait is a beacon of freedom in the Gulf," Nadim Houry, deputy Middle East director at Human Rights Watch, said.
"The appeals court should overturn the convictions imposed for peaceful speech-related crimes."
Kuwait's Information Ministry said on Monday it backed free speech but authorities must enforce the law.
"Authorities should suspend and then abolish laws that criminalize peaceful criticism of public officials because they violate international human rights standards," HRW's Houry said.
The United States and Amnesty International have also called on Kuwait to respect freedom of expression.
On Tuesday a Kuwaiti court sentenced three former opposition lawmakers to three years in jail for comments deemed offensive toward the ruling emir made at a public gathering, the second such conviction in less than a week.
The three ex-lawmakers - Islamists Falah al-Sawwagh and Bader al-Dahum, and populist Khaled al-Tahus - were arrested in October after an opposition-led protest where riot police used teargas and stun grenades.
Tens of thousands joined similar protests in October over changes to an electoral law passed by the emir, who is described as "immune and inviolable" in the constitution and shielded from public criticism by the penal code.
The emir said the old voting system was flawed and that his changes to the voting system were necessary for security and stability. Opposition MPs said the changes, made six weeks before the election, would limit their prospects and boycotted the vote.
Another high-profile trial is expected to continue next week. Opposition politician Musallam al-Barrak has been charged on three counts related to a speech in October in which he made remarks deemed insulting of the 83-year-old emir.
The US ally and major oil exporter has been taking a firmer line on politically sensitive comments in recent months. On Sunday it sentenced a political activist to five years in prison for insulting the emir on Twitter.
Kuwait allows more dissent than other Gulf states and has avoided the kind of mass unrest that unseated four heads of Arab states in 2011.
The electoral changes, however, triggered some of the biggest protest marches in Kuwait's history and calls for political reform.