As party leaders fight for the 'Christian vote', UKIP are promising to extend protections for those who disagree with same-sex marriage, and "uphold robustly the rights of Christians" all over the UK.

In the foreword to his 'Christian manifesto', Nigel Farage says Britain needs "a much more muscular defence of our Christian heritage and our Christian Constitution".

"Sadly, I think UKIP is the only major political party left in Britain that still cherishes our Judeo-Christian heritage," he writes. "I believe other parties have deliberately marginalised our nation's faith, whereas we take Christian values and traditions into consideration when making policies."

The manifesto outlines where UKIP stands on "Christian issues" such as freedom of worship, religious education, welfare and immigration, and pays particular attention to gay marriage. The party promises never to "discriminate against traditional marriage" and to extend "reasonable accommodation" to ensure that Christians in particular are not penalised for their beliefs.

It criticises the legalisation of same-sex marriage in the UK. However, a UKIP government would not repeal the legislation "as it would be grossly unfair and unethical to 'un-marry' loving couples or restrict further marriages, but we will not require churches to marry same-sex couples."

The principle of reasonable accommodation, which would allow workers the right to refuse tasks which conflict with their religious beliefs, has polarised political and legal opinion in recent months. In Northern Ireland, it has been highlighted by the Ashers Bakery case, where the owners refused to bake a cake with a slogan in favour of gay marriage.

In response, DUP MLA Paul Givan tabled a religious conscience clause bill, which has been condemned as "nothing but a thinly veiled attempt to legalise discrimination against LGB people," by Green Party MLA Steven Agnew.

Irish republican party Sinn Fein also vowed to oppose Givan's bill. A spokesperson for the party said that it was "opposed to any dilution of equality legislation" while the director of the Rainbow Project, a gay rights charity in Northern Ireland, accused Givan of promoting "hostility" against LGBT people.

Other parts of UKIP's 'Christian manifesto' are also likely to divide opinion, even among those it seeks to appease. Many Christians have spoken out against the party's immigration policies, and though the manifesto promises to "take our fair share of refugees", Farage suggested just last week that the UK make a "gesture" by giving refugee status to a few people – notably Christians – and send the rest "back to where they come from". At a hustings several days later, Labour candidate and Christian Gavin Shuker branded these comments "outrageous".

UKIP has also pledged to reduce overseas aid spending because "charity should begin at home".