A Catholic peer has delivered a blistering attack on the government for disregarding the plight of Christian Syrian refugees while prioritising Muslims and gay people.

Lord Alton of Liverpool accused ministers of running a flawed refugee policy which is "one-size-fits-all" and fails to adequately protect Christians fleeing ISIS. He argued that Christians "who represent no threat to this country" are given the same opportunity as "marauding young men" who assaulted more than 500 German women on New Year's Eve.

The peer joined a number of other Christian peers including the Archbishop of Canterbury in expressing concern that the government's relocation scheme only takes refugees from UNHCR camps while ignoring Christians who largely avoid the camps for fear of violence.

"If gay people (rightly) qualify as 'vulnerable' then Christians should too," he wrote in a letter to Home Office minister Lord Bates over Christmas.

"You will know of the considerable weight of evidence of assassinations by ISIS of Church leaders; mass murders; torture, kidnapping for ransom in the Christian communities of Iraq and Syria; sexual enslavement and systematic rape of Christian girls and women; forcible conversions to Islam; destruction of churches, monasteries, cemeteries, and Christian artefacts; and theft of lands and wealth from Christian clergy and laity."

He told Lord Bates that the "complicated administrative procedure" employed by the UK government meant that in reality Christians were excluded from the chance of resettlement.

In reply, Bates insisted the government did not "discriminate" on the basis of religion and encouraged Christians to register as refugees in order to seek possible resettlement.

However Alton said afterwards the government's "obsession with 'non-discrimination'" makes "no sense", according to Catholic Herald.

"It's far, far worse than discrimination – a campaign of total annihilation is underway, which is why these minorities should be discriminated in favour of," he added.

"Of course we should discriminate in favour of those most at risk, not least because we have a duty to protect the most vulnerable.

"Instead of creating a false even-handed dichotomy British policy should actively search out, and be weighed in favour of, those who are suffering the most: those who are on the receiving end of the very worst of ISIS's campaign of beheadings, unspeakable violence, forced conversions, rape, and dispossession of homes, livelihoods and thousands of years of faith, culture and identity."

David Cameron, who has previously expressed support for Christian refugees in Syria and Iraq, did not reply to a previous letter sent by Alton in September. The letter called for Christians to be actively included in the 20,000 refugees set to be resettled in the UK by 2020.