An amendment to the Marriage (Same Sex Couples) Bill concerning humanist marriage ceremonies has been withdrawn during the third and final reading of the bill, after the attorney general warned that it would fall foul of the European Convention on Human Rights (ECHR).

Today MPs in the House of Commons debated the bill put forward by the Humanist Association, which proposes to allow recognised groups to officiate at marriage ceremonies.

Dominic Grieve, the attorney general, raised the objection that the amendment would fall foul of the ECHR as any “belief organisation” would be able to claim they were being discriminated against if they weren’t able to perform marriages.

He originally suggested that this could include “Tiddly-winks” societies, but later debate focused on the possibility of allowing Pagan or spiritualist marriages, which was broadly opposed by the House.

Mr Grieve said: “I am highlighting that there is a serious defect in the amendment that has been presented to this House, because it would have the consequence – which I think is quite obvious when you look at it – that because of the discriminatory nature of the favour it gives to humanists, as opposed to other secular organisations, that it would have the consequence of making it incompatible with the [ECHR] rights.”

Shadow Equality Minister Kate Green, who tabled the bill, said it would be “utterly irresponsible” to ignore the possibility, but decried Mr Grieve for not raising the matter earlier.

Labour sources had told PinkNews that they would drop their support for the motion if humanist marriages were discussed at a later date, after the attorney general’s advice is given to the House of Lords.

A government source told PinkNews they believe there is broad agreement in the House not to proceed with an amendment that could open up marriage to Pagan and Jedi marriage.

At the moment, anyone taking part in a humanist ceremony must still have their marriage made legal through a register office.

However, humanist ceremonies have been a fully legal form of marriage in Scotland since 2005. It is one of only six nations in the world to allow them.

During the debate Peter Wishart of the Scottish National party (SNP) pointed out that humanist weddings are now the third most popular form of wedding in Scotland.

Mr Grieve warned that the amendment would create “a wide range of consequences including creating a need for a completely new system of registering marriage and a new system of authorising celebrants.” He went on to say that the Pagan Federation and the White Eagle Lodge had been able to register to conduct legal marriage in Scotland since humanist weddings became legal.

Lib Dem MP Stephen Williams responded that only belief organisations with charitable status would be able to legally marry people, ruling out “Jedi Knights” and other groups.

It was then pointed out that Freemasons have charity status, and so may be able to perform marriages under the amendment. The remark was made by Sir Tony Baldry, who is himself a Freemason.

Tory MP Crispin Blunt said he was “astonished” by the claim that extending human rights to a group could fall foul of human rights conventions.

Andrew Copson, chief executive of the British Humanist Association, said: “The amendment does not open up legal recognition for any new weddings other than humanist ones.

“Humanist weddings are popular and meaningful and legal recognition for them would be fair, timely, and not at all controversial.”

Liberal Democrat MP Stephen Gilbert was a supporter of the amendment.

Writing for PinkNews.co.uk, the MP said: “The prime minister may have to accept that there are likely to be majorities in the House of Commons for opposite sex civil partnerships, humanist weddings as well as equal marriage for gay and lesbian people. He should welcome these changes.”

But Conservative MP Sir Tony Baldry said the humanist weddings plan was “not a particularly sensible amendment, whichever side of the argument you’re on”.