Five US senators have warned that the trial of Finnish politician Päivi Räsänen could open the door for a "secular blasphemy law" against Christians, Muslims and Jews expressing countercultural views on marriage and sexuality.

The Republican Senators sent an open letter to the US Ambassador-at-Large for International Religious Freedom, Rashad Hussain, on the day of the Christian Democrat MP's trial in Helsinki this week.

Dr Räsänen, a former Interior Minister, pleaded not guilty in Helsinki District Court on Monday to three criminal charges of "ethnic agitation" for sharing her Christian beliefs in a pamphlet on marriage in 2004, comments she made on a radio show in 2019, and a tweet with a picture of a Bible passage from Romans 1 condemning homosexual practice.

Evangelical Lutheran Bishop Juhana Pohjola, who is on trial for publishing the marriage pamphlet and keeping it posted on his church's website, also pleaded not guilty to hate crime.

Senators Marco Rubio, James Lankford, Josh Hawley, Mike Braun and James Inhofe told Ambassador Hussain: "We are greatly concerned that the use of Finnish law is tantamount to a secular blasphemy law. It could open the door for prosecution of other devout Christians, Muslims, Jews and adherents of other faiths for publicly stating their religious beliefs that may conflict with secular trends.

"We believe that, regardless of whether Finnish prosecutors agree with the religious beliefs that MP Räsänen and Bishop Pohjola have expressed, all people have a fundamental right to the freedoms of religion and speech, which should be upheld without fear of government interference."

The Senators urged Mr Hussain, who in December became the first Muslim US Ambassador for International Religious Freedom, "to raise these concerns with the Finnish government as proceedings continue against MP Räsänen and Bishop Pohjola, condemn these unjust prosecutions, and continue to monitor other developments that threaten religious freedom in Finland and Europe".

They concluded: "We greatly appreciate the longstanding and positive relationship between the United States and Finland. Our countries enjoy significant historic, cultural, economic, and security ties that speak to the values that we both share.

"This is precisely why we are concerned with these alarming developments that stand to weaken Finland's longstanding commitment to the bedrock rights of freedom of speech and freedom of religion."

According to ADF International, which is defending Dr Räsänen and Bishop Pohjola, the court is due to hear the closing arguments in the case on February 14 with a ruling expected in early March.

If convicted under the Finnish criminal code's section on "war crimes and crimes against humanity", they could face a two-year prison sentence. But in an interview with Christian Today in December, Bishop Pohjola said the most likely penalty would be a fine.