It began with heretical Sunday ferry sailings to the Western Isles and has now metamorphosed into a row which is pitting a Daily Mail columnist and Christian campaigner against a former pop songwriter turned fundamentalist politician and preacher.

But the battle for the soul of the remote Western Isles is anything but Christian, as bitterness grows on both sides.

The roots of the battle lie in the decision to run Sunday ferries to Stornoway and Lewis, which outraged Christian islanders. Ironically, it has also turned religious figures against each other.

On one side there’s the Reverend George Hargreaves, the London-based leader of the Scottish Christian Party, and on the other there is John MacLeod, a controversial journalist and promoter of Christian values. Both men want a Christian MP in the Western Isles seat and they are locked in a furious debate about who that should be.

MacLeod derides Hargreaves as a “carpetbagger”, muscling uninvited into a local debate; while Hargreaves says MacLeod isn’t taken seriously by the religious community on the islands.

The Mail journalist has used the local press to launch stinging attacks on his opponent. One of his letters to the Hebridean Times said: “Rev George Hargreaves has no credibility here, nor any authority to strut up frae awa’ o’er the Border and graciously offer to mount a political campaign on our behalf.”

The row began when Hargreaves’s party announced its intention to stand in the Western Isles, running its campaign on the back of anger over the decision to allow Sunday sailings from Stornoway.

Hargreaves, who became rich after writing Sinitta’s 1980s gay anthem So Macho and its B-side, Cruising, intends to use the Western Isles to “throw down the gauntlet” and press for a Christian voice in Scotland’s corridors of power.

MacLeod, a controversial writer who once claimed in a column that Holly Wells and Jessica Chapman would not have been murdered in Soham by Ian Huntley if they’d “kept the Lord’s day”, claims Hargreaves is an outsider and has called for an independent Christian candidate to send Hargreaves packing.

His letter-writing campaign questions Hargreaves’s wish to represent the community and accuses him of carpet-bagging. He also claimed Hargreaves was committed to right-wing policies on the “same continuum” as UKIP.

MacLeod added: “Hargreaves is a demagogue ... He’s charming, very warm, faintly intimidating and has a tin ear, interrupts mercilessly, harangues, lectures.”

Hargreaves, who said his mission was to represent islanders’ opinions, stated: “We decided to start our campaign because of a Pearl Harbour raid on the island, a sneak attack against the wishes of the island, which was the start of CalMac’s ferries on a Sunday. If an island doesn’t want ferries on a Sunday, they shouldn’t have them ... John MacLeod is miffed because he wanted to put an independent candidate on the Western Isles and knows he has no chance of doing that if we stand.”

He added: “John’s style of writing is very acidic, toxic in many respects, because he shoots from the hip and thinks later. I don’t think people take him seriously on the islands. I’ve asked about, and he has very little support.”

Hargreaves claims significant support in the constituency, backed by a poll in the Stornoway Gazette in which 75% of respondents said his party had a chance of winning. But the poll’s accuracy has been questioned, after an email shown to the Sunday Herald purported to reveal that the party had sent a round-robin message to all its supporters, asking them to contribute to the poll.

In the last European election, the Scottish Christian Party took 9% of the vote in the constituency, coming third behind SNP and Labour.

The Western Isles seat is currently held by the SNP’s Angus MacNeil, who has lost his authority among the islanders after a sex scandal which forced him to admit to engaging in “heavy petting” with two teenagers. This has left a political vacuum Hargreaves hopes to fill.

However, some on the islands agree with the decision to run Sunday ferries.

Donald John MacSween, Labour’s candidate for the seat, said: “The polling booth will reflect just how out of touch Rev Hargreaves is from 21st-century Hebridean life. I recall the harbingers of doom, like Rev Hargreaves, proclaiming that the introduction of Sunday flights would destroy our island culture. Sunday flights have been with us for years now and who has noticed, apart from those who need to use the service?

“Committed Christians, whom I deeply respect, have quietly used this service but this does not affect their effective witness.”