Dr John Sentamu says government should not alter centuries-old social structures, but rights campaigner accuses him of being 'religious authoritarian'

The government should not overturn centuries of tradition by legalising gay marriage, the archbishop of York has said.

Dr John Sentamu, the second most senior bishop in the Church of England, said the church did not object to the introduction of civil partnerships in 2004, but that marriage should only be between men and women.

"If you genuinely would like the registration of civil partnerships to happen in a more general way, most people will say they can see the drift," he said. "But if you begin to call those marriage, you're trying to change the English language."

The archbishop's comments, which were denounced by the gay rights campaigner Peter Tatchell, precede the start of the government's consultation on gay marriage in March.

Sentamu said it was not the role of the government to alter social structures that had been in place for centuries.

"I don't think it is the role of the state to define what marriage is. It is set in tradition and history and you can't just [change it] overnight, no matter how powerful you are," he told the Daily Telegraph.

"We've seen dictators do it in different contexts, and I don't want to redefine very clear social structures that have been in existence for a long time and then overnight the state believes it could go in a particular way."

Tatchell, the co-ordinator of the Equal Love campaign, said: "Archbishop Sentamu is a religious authoritarian who wants to impose his personal opposition to same-sex marriage on the rest of society.

"It is not a Christian value to demand legal discrimination against gay couples and to treat them as inferior, second-class citizens with fewer rights than everyone else."

The issue of homosexuality is divisive in the Church of England. Sentamu expressed concern over the "gay marriage" of homosexual clergy after two ministers exchanged rings and vows at a service in London in 2008.

In a joint statement with the archbishop of Canterbury, Dr Rowan Williams, he said: "Those clergy who disagree with the church's teaching are at liberty to seek to persuade others within the church of the reasons why they believe, in the light of scripture, tradition and reason, that it should be changed. But they are not at liberty simply to disregard it."

Sentamu, who fled Uganda in 1974, also said the church was failing to represent black and working-class Britons. He said: "The church should be a sign of the kingdom of heaven and should be telling us what it will look like.

"Heaven is not going to be full of just black people, just working-class people, just middle-class people – it's going to be, in the words of Desmond Tutu, a rainbow people of God in all its diversity."

The murder of Stephen Lawrence in London in 1993 had forced many organisations to address institutional racism, Sentamu said, but others – such as media and football – had failed to be so effective, he added.

"Football never did it, so I'm not surprised [by allegations of racism on the pitch]," he said. "I didn't hear that the media ever said: 'Let's put a mirror to ourselves and see whether there isn't this tendency of stereotyping, or being prejudiced, of advantaging people because they went to the same school.'"