The Free Church Assembly yesterday maintained its stance against the singing of Christmas carols and hymns, rejecting this as transgressing its traditional purity of worship.

It turned down a move by the Presbytery of Edinburgh to set up a special committee to investigate traditional forms of worship and the exclusive use of unaccompanied psalm-singing in the church service.

The controversy arose after Bon Accord Free Church, Aberdeen held a carol service last December. The minister, the Rev Iver Martin, told the Assembly the carol service was part of an Outreach move to attract those who might never enter a church except at Christmas. Aberdeen Free Church otherwise held traditional English and Gaelic services.

The Assembly backed the Presbytery of Lewis who urged the Church to uphold its traditional purity of worship and continue singing psalms. The Rev Kenneth Stewart of Stornoway Free Church told the Assembly carol singing ''crossed the line'' of such purity. He said: ''I feel strongly that the holding of what we consider to be a carol service would cross that line. We must not use evangelism as an excuse to opt out of our principles of public worship.''

Mr Kenneth Maciver, an elder in Bon Accord Church session, told the Assembly: ''We decided to hold a carol service in the church. We wanted to tell people round about the Free Church what we were about. We wanted them to get a flavour of our church.''

He said up to 4000 leaflets were distributed in Aberdeen inviting people to the carol service. Several hundred people attended. Some said they had never before attended church. Many returned or sent their children to the Sabbath school.

Mr Maciver called on the Free Church to be flexible. He added: ''The Free Church must not vote to shut the door on the thousands of unchurched masses in the cities.

''All I am asking is a bit of leeway. I am not afraid of God's displeasure for singing carols''.

The Assembly, however, voted to adhere to the traditional forms of worship using only the Psalms.

Mr Martin said: ''Perhaps carol singing did cross the line.''

The Assembly decided not to debate the question of moving the Free Church HQ on the Mound to Inverness. The matter will be discussed at presbytery level.