Campaigners have denounced Donald Trump’s vow to repeal a law that stops religious groups endorsing or campaigning for political candidates – claiming it would damage both America’s democracy and its houses of worship.

Speaking at a National Prayer Breakfast in Washington DC, the US President said he would “totally destroy” the Johnson Amendment, a piece of legislation dating from 1954. The provision threatens churches and other religious institutions with the loss of their tax-exempt status if they “campaign from the pulpit”.

“I will get rid of and totally destroy the Johnson Amendment and allow our representatives of faith to speak freely and without fear of retribution,” said Mr Trump.

Trump pledges to destroy Johnson amendment

He added: “Jefferson asked, ‘Can the liberties of a nation be secure when we have removed a conviction that these liberties are the gift of God’. Among those freedoms is the right to worship according to our own beliefs.”

But activists fighting to retain America’s separation between church and state, have condemned the remarks, saying the move would open the way to a flood of money entering politics through unregulated, tax free churches. They also claim polls show an overwhelming majority of people – along with members of the clergy – do not want the law repealed.

“If the law is repealed, it would lead to the funnelling of money into political campaigns with no way to check,” Rob Boston, Director of Communications for the Americans United for Separation of Church and State, told The Independent.

Mr Boston said polls showed most Americans did not support repealing the law. He cited a surgery carried out last year by LifeWay Research, which found that 79 per cent of people thought pastors should not endorse candidates during a church service.

He said he believed the move had had been pushed on Mr Trump by members of the religious right, including Jerry Falwell Jr, the president of the largest Christian college in the world and a key supporter of the New York tycoon. He said Mr Falwell’s father, a major religious leader, had fallen foul of the law during the 1980s.

Mr Boston said he believed the move could also detrimentally affect America’s houses of worship. “There are a number of reasons why people go to a place of worship. But rarely are they looking for guidance on who to vote for,” he said.

Steve Benen, a political writer and blogger, wrote on MSNBC: “Why does Trump want to change this? Basically because the religious right told him to. But why does the religious right want this? Because some on the right still dream of creating a church-based political machine.”

Rabbi Jack Moline, President of the Washington-based Interfaith Alliance, said that Mr Trump’s claim that the clergy were too afraid to speak openly, was a “lie that has been advanced for years by the religious right”.

“President Trump's attack on the Johnson Amendment, if successful, would undermine religious freedom by plunging houses of worship into partisan politics and inviting the rewards and punishments of patronage,” he said.

“What’s more, houses of worships would become conduits for unregulated “dark money” in elections, with no restrictions or disclosure requirements.”

At the gathering of religious leaders in the nation’s capital, Mr Trump also joked about the poor ratings of Arnold Schwarzenegger since he took over as host of The Apprentice.

He also defended his recent executive order on immigration, decrying “generous” immigration policies and arguing that there were people who sought to enter the country “for the purpose of spreading violence or oppressing other people based upon their faith.”