Pressure is mounting for Sunday sailings to Lewis ahead of the introduction of cheaper ferry fares to the Western Isles this autumn, a meeting will hear this week.

The board of Caledonian MacBrayne, the ferry operator, will consider whether a controversial Sabbath service should begin when it meets tomorrow - three days after an unscheduled sailing to the island on Easter Sunday.

The Scottish Government's decision to pilot Road Equivalent Tariff (RET) on services to the Western Isles makes it more likely that CalMac directors will opt to schedule seven-day operations on both its Stornoway to Ullapool route and Tarbert (Harris) to Uig (Skye), the only two major CalMac services now without a Sunday sailing.

Cuts of up to 50% on ferry fares to North and South Uist, Lewis, Harris, Barra, Coll and Tiree are expected when the RET pilot begins in the autumn, making trips to the islands more financially attractive. This will pose a problem on the two six-day routes where capacity is already an issue. The only obvious way to provide additional spaces is to sail seven days a week.

As The Herald revealed in November, the Scottish Government will not intervene. Stewart Stevenson, the Transport Minister, has already decided that he will leave the final decision to CalMac, despite the strength of religious feeling on the issue.

The Lord's Day Observance Society (LDOS) has submitted a petition bearing almost 4000 signatures out of a population of just over 20,000 in Lewis and Harris. However, there is also a strong body of support for ferries seven days a week.

CalMac's communications director Hugh Dan MacLennan said yesterday: "I can confirm that Sunday sailings will be discussed by the board at Wednesday's meeting in Gourock. The board will discuss it in the context of the RET pilot and its implications for services to the Western Isles. No paper is being presented on the issue and there are no recommendations to the board."

Meanwhile, he said the ferry Isle of Lewis had to make a return crossing on Easter Sunday to clear the logjam of traffic that had built up due to disruption to services with the storms at the end of last week.

"We managed a sailing on Saturday afternoon but we had lost all Friday's sailings and Saturday morning's as well. So on Sunday we had to make another crossing.

"We took eight articulated lorries to Ullapool and 11 back to Lewis, plus a car. We would not have sailed on Sunday had it not been for the disruption last week, but we have been thanked for making this extra effort."

The Rev Andrew Coghill, the Church of Scotland minister at Leurbost who is the vice-chairman of the Lewis branch of the LDOS said: "I was not aware of the sailing yesterday."

But it didn't affect his and others' stance against a Sunday sailing: "The secretary of the LDOS has written to CalMac drawing attention again to the strength of our own petition in November and the weakness of the online petition of the opposition, which is one of their (supporters of a Sunday sailing) major planks."

He said that there were questions about the integrity of the e-petition as at least 200 signatories of the e-petition were anonymous, there was duplication and it could be signed anywhere in the world.

But as of yesterday the e-petition was claiming 1346 signatories. One of the last said simply: "What are people scared off happening? Opening the pubs and flights didn't cause too much distress. I don't think you would have too many lorries roaring through the streets on a Sunday as the hauliers have to pay their staff more on Sundays. Northern Isles and the rest of the Hebrides seem to have a normal Sunday why can't we?"