Britain's black majority church leaders are attempting to mobilise hundreds of thousands of voters in the general election in a bid to influence the outcome and as a "mandatory" part of Christian faith.

Ethnic minorities now make up eight per cent of the electorate and people of African and Caribbean heritage make up a significant proportion of this group, according to the first ever Black Church manifesto.

Operation Black Vote, set up in 1996 to mobilise black and ethnic minority political engagement, has identified 168 marginal seats in which the Black and Minority Ethnic (BME) vote could decide who wins and who loses.

"With such a high number of Christians among Black communities, the BMC [Black Majority Church} in Britain is set to have a significant say in who wins this next election," the manifesto says.

Voter registration among the black community has historically been poor, which means the political power of the Christian black majority constituency remains untapped.

"This manifesto forms part of an attempt to mobilise people in the Black Church and the wider community so that their voice is heard by our political leaders. We do not see political engagement as optional. Rather, we see it as a mandatory part of our Christian faith as responsible citizens in accordance with biblical teaching," the manifesto states.

Published by the National Church Leaders Forum, which represents hundreds of thousands of British Christians in the black majority churches, the manifesto is written by Pastor Matthew Ashimolowo, founder and senior pastor of Kingsway International Christian Centre, Rev Nezlin Sterling, former General Secretary of the New Testament Assembly, Bishop Eric Brown, former Administrative Bishop of the New Testament Church of God and Pastor Agu Irukwu, chair of the phenomenally fast-growing Redeemed Christian Church of God.

The preface, to the document, titled Black Church Political Mobilisation: A Manifesto for Action, describes it as the first document of its kind for the Black Church in Britain. It notes that black majority churches are often regarded as the most cohesive part of the black and minority ethnic communities.

"Although relations between the police and BME communities have been historically poor, they are improving and BMC leaders should encourage their members to consider the Police Service as a career choice," the manifesto says, outlining areas of concern to BME voters when considering why they should vote and who for. For example, even though black people make up between two to three per cent of the population, they constituted 15 per cent of those who were stopped by the police in 2008/09. And on average, five times more black people than white people in England and Wales are in prison.

Among the concerns are the disproportionate number of BME people in the country's prisons, the disproportionate numbers affected by poor mental health, the importance of family and marriage as "gifts from God", and more effective engagement with media, music, arts and culture. Black Caribbean and Black African men aged 13 to 24 years have the highest suicide rate of any group.

The Black Church leaders also call on the Government to examine the conditions it attaches when giving aid to poorer countries "that might be perceived as displaying attitudes of residual imperialism and cultural hegemony, undermining the recipient nation's sovereignty and cultural values". And it urges BME Christians to match or exceed the Government's donation of 0.7 per cent of their income to overseas aid and development as an integral part of their Christian commitment to the poor.

According to Ethnic Minority British Election Study, 68 per cent of BME voters supported Labour in 2010, compared with 16 per cent for the Conservative and 14 per cent for the Liberal Democrats. Traditionally, BME voters have supported Labour, believing that the party better represents their concerns around issues like unemployment and discrimination, the manifesto says. However, the BME vote for Labour in 2010 was down from that of 2005. The manifesto says this trend is expected to continue.

The manifesto has been launched in a contest where African and Caribbean churches are growing fast. In London alone, 48 per cent of churchgoers in 2012 were black Christians, up from 44 per cent in 2005, a higher increase than for any other ethnic group. In the capital city there are a number of mega churches, including Ruach led by Bishop John Francis, New Wine Church led by Pastor Michael Olaware and Jesus House led by Pastor Agu Irukwu.

In 2006, the then Prime Minister Tony Blair spoke at Ruach and Prince Charles and the Duchess of Cornwall visited Jesus House in November 2007.

Quoting 1 Chronicles and Matthew 5, the manifesto says: "This is the first time we have produced a document like this to mobilise the Black Church constituency. We want our churches to fully engage with the wider socio-political issues it raises in the hope that, like the men and women of Issachar, we will better 'understand the times' and know what we must do to be 'salt and light' in our communities."

The importance of the black majority churches, not just in this election but in wider society, is being recognised by all the parties. David Cameron, a member of the Church of England, recently paid his first ever visit to the Festival of Life at ExCel London, the UK's largest inter-denominational Christian gathering organised by the Redeemed Christian Church of God. During an eight minute address, he spoke about aspiration, the big society and religious freedom. "I believe in aspiration. I believe the only limit to someone's potential is their own ambition and talent and I look out into this crowd and I can see someone who will hold my role and become prime minister of this great country," he said.

A few days later, Labour leader Ed Miliband visited the black majority church Praise House in Croydon and pledged support for religious expression, religious freedom, faith schools and religious groups running community projects. He pledged to address issues of food poverty, benefits delays, low pay and to abolish the bedroom tax. He also promised action on climate change and the environment.