As a witness to the Public Bill Committee of the House of Commons, which is scrutinising the government’s same-sex marriage bill, leading barrister and supporter of same-sex marriage, Lord David Pannick QC said it would take a “legal miracle” for religious bodies to be forced to conduct same-sex marriages in the UK.

Lord Pannick appeared in front of the committee on Tuesday morning alongside his fellow Queen’s Counsel, Baroness Helena Kennedy.

He submitted written evidence to the committee and stated: “For the European Court of Human Rights to compel a religious body or its adherents to conduct a religious marriage of a same-sex couple would require a legal miracle much greater than the parting of the Red Sea”.

Opponents of same-sex marriage have argued that even with “quadruple lock” protections to allow churches not to opt-in to performing weddings for same-sex couples, religious bodies that don’t opt-in may still be sued in the European Court of Human Rights.

Lord Pannick said he believed any case that tries to sue a religious institution which had not opted-in to performing marriage ceremonies for same-sex couples would be “absolutely hopeless, and it will be hopeless in 10 years’ time as well.”

In response to fears that legal actions against teachers could occur, possibly in their thousands according to the anti-gay Coalition for Marriage, he said: “The teacher already has protection. If he or she does not, then something should be done about it. They do have protection now, and they will not have less protection under the bill.”

Baroness Kennedy said: “We are not saying that there will be no attempts to mount legal actions – we suspect there will. However, the view is solidly held that these would not be successful.”

She added that she felt that although there was a chance legal actions could be successful, the law itself was clear and the success of legal claims would depend on “juries and not judges.”

Questioned by Tory MP Tim Loughton about grey areas between religious and public policies, such as the speculation that schools could refuse churches the right to use their property if they did not support equal marriage, Lord Pannick said he had “no doubt whatsoever” that courts would rule in the church’s favour.

Both Lord Pannick and Baroness Kennedy said they had “no problem” with the idea of extending civil partnerships to heterosexual couples.

Labour MP Chris Bryant pointed out that as the law stands, same-sex couples are allowed to play religiously-themed music tracks such as “Stairway to Heaven” in civil ceremonies but heterosexual couples are not.

Baroness Kennedy responded jokingly that she would “make it [her] life’s work” to campaign against “musical discrimination”.