The Scottish branch of Anglicanism has taken a major step towards allowing same-sex marriage in an historic vote but one which will reignite tensions within the fractured worldwide church.

Members of the General Synod of the Scottish Episcopal Church voted overwhelmingly for a proposed change to its ecclesiastical law to redefine marriage by removing references to it being “of one man and one woman”.

If the change is confirmed in a further vote next year, it would make Scotland the first part of the British Isles in which gay and lesbian couples can marry legally in a church using Anglican rites.

But the move would almost certainly see the Episcopalians partially excluded from bodies of the worldwide Anglican Communion in the same way as the US branch, the Episcopal Church (Tec), which has already changed its canon of marriage to include same-sex couples.

It could have major implications for the future of the estimated 80 million-strong global Anglican communion just six months after a gathering in Canterbury of bishops and archbishops from almost 40 countries appeared to have averted a permanent schism over sexuality.