The Board of Deputies has warned of the "detrimental effect" on religious life if plans to make dawn and dusk an hour later are adopted.

A government tourism strategy, to be published this week, is expected to support changing the clocks, resulting in longer summer evenings but darker winter mornings.

But the Board says this would make it impossible for many Orthodox Jews to pray in a morning minyan before work in winter, hit Shabbat and festival celebrations and even mikveh attendance for women.

Any change would force "many Jews to end generations of religious practice," it wrote in a position paper.

A Private Member's Bill extolling the benefits of an extra hour of evening daylight has been introduced by Tory Rebecca Harris backed by road safety groups which say it would save lives.

But the Board said a similar experiment in the 70s severely affected the ability of many to "practise religion".

Many observances have to be performed at certain hours of the day determined by sunrise and sunset.

Because the morning service must be recited in the first quarter of the day after sunrise, most Jews who want to can now get to a minyan before work. But many men would find it hard to do so in winter if sunrise were an hour earlier. Not being able to pray in a minyan would prevent some saying Kaddish, the Board points out, causing "major distress at a time bereaved families are already vulnerable".

An extra hour of evening daylight would make it "impossible" for children to stay up for the start of Shabbat in summer: delay the beginning of the Pesach Seder and stop women going to a mikveh until 1am in the summer because they may only go after sunset. Chanoch Kesselman, executive co-ordinator of the Union of Orthodox Hebrew Congregations, said he hoped that opposition to darker winter mornings in Scotland would be sufficiently strong that the proposal woud fail.

Leah Granat, deputy director of the Scottish Council of Jewish Communities, said: "Concerns have been expressed to us that Shabbat even as far south as Glasgow would not end until 12.45am during the summer, and not until an hour after that in northern Scotland.

"Others have, however, pointed out that the effect of Shabbat beginning in mid-afternoon in the winter is also potentially difficult."