The General Synod moved a step closer to banning clergy from membership of groups such as the British National Party (BNP) when it gave final approval to the Clergy Discipline (Amendment) Measure this afternoon.

The Measure doesn't itself proscribe membership of the BNP, but gives the House of Bishops power to declare, by a two-thirds majority, that an organisation's "constitution, policies, objectives or public statements . . . to be incompatible with the teaching of the Church of England in relation to the equality of persons or groups of different races".

The Measure will require parliamentary approval and royal assent before the Bishops could make such a declaration, which will then need to be approved by the General Synod.

The move gives effect to a private member's motion from Vasantha Gnanadoss (Southwark), which the Synod passed in 2009, calling for membership of such organisations to be banned.

The Bishop of Guildford, the Rt Revd Christopher Hill, said: "The Synod itself would have the opportunity to endorse or otherwise a decision by the House of Bishops to proscribe membership or support of a racist organisation in relation to the clergy." This "important change in relation to racist organisations" was a "faithful response to what you - the Synod - asked us to do".

In addition, the Measure also amends the way clergy convicted of criminal offences can be dealt with under the Clergy Discipline Measure, enabling bishops to bring disciplinary proceedings against clergy convicted of certain offences abroad, and for serious offences where a priest has not been sentenced to a term of imprisonment.