Willie Rennie, the Scottish Liberal Democrat leader, has attacked Catholic bishops for seeking to “impose” their views on gay marriage.

Speaking on Saturday to the Scottish Liberal Democrat party conference, he said that Catholic bishops’ moves to scupper gay marriage plans were “an affront to liberal democracy”.

Since the government announced a consultation on the issue last month, faith leaders have spoken out strongly against it, claiming that the SNP will lose the support of 800,000 Catholics.

Glasgow archbishop Mario Conti has written to all Scottish parishes to urge them to oppose marriage equality.

He said that churches would “actively campaign” to block marriage rights for gay people and warned that the move would create “larger divisions” in society.

Bishop of Paisley Philip Tartaglia wrote to first minister Alex Salmond last week to warn that the consultation would lead to a “serious chill” between the government and the Catholic Bishops’ Conference.

According to the Scotsman, Mr Rennie said: “What is unacceptable to liberals is the control that some leaders of the Catholic Church are seeking to exert over the people of the Catholic faith.

“To threaten to invoke some sort of block vote is an affront to liberal democracy and one that we must challenge. Many individual Catholics have told me they will not be following their leaders against the issue of equality for same-sex marriage.

He added: “We are not imposing anything on the church, so what I find difficult is that they want to impose on everyone else. A liberal Scotland is where everyone can have their own freedom of thought and belief.”

Announcing the consultation at the beginning of September, deputy first minister Nicola Sturgeon said ministers believe “that no religious body or its celebrants should be required to carry out same sex marriages or civil partnership ceremonies”.

The consultation will ask stakeholders whether churches should be given the option of holding the ceremonies if they wish.

A gay marriage consultation launched by the Westminster government will only look at civil marriage, despite calls from gay rights campaigners and smaller faiths for it to consider religious ceremonies.