Savvy shoppers in the north have been buying in bulk to take advantage of loss-leading offers from the big supermarkets.

Sainsbury's rejected one online order for 600 bottles of Kedem grape juice being sold at half-price. But it did not restrict shoppers at its stores, where empty shelves bore testimony to its north of England depot being unable to meet demand for matzah, grape juice and other soft drinks on offer.

At the Heaton Park branch in north Manchester, a Prestwich father-of-one was buying up 134 bottles of grape juice. The man, who declined to give his name, said he was taking advantage of the offer to make savings on a year's supply for his family and two other households.

"We always bulk buy to save money. We can't afford to live another way. When I found out about the offer, I went down to Sainsbury's straight away."

Branch manager Aiden Hale said the store was experiencing record sales of kosher goods."We've been taking moves to ensure that our shelves can be restocked."

We always bulk buy to save. We can't afford to live another way.

Also in north Manchester, Prestwich mother-of-four Esther Selouk was eyeing the deals at Cheetham Hill Tesco. Supermarket offers were a big draw.

"No one wants to spend more than they have to. But I always buy from the kosher shops, partly out of loyalty, but also because the supermarket shelves can get mixed up with non-Pesach stuff. I know in a kosher shop it's 'kosher for Pesach'."

Richard Hyman, owner of Manchester's longest established kosher shop, Titanics, feared mass buying of supermarket offers could detrimentally affect the kosher market over the year.

Titanics staff have been busy packing 500 Pesach food orders, many for its national Passover delivery operation, serving customers from communities including Portsmouth, Hull, Inverness and Anglesey. Some may have been amused by its website's joking offer of "Pesach bread".

Mr Hyman reported that online sales were holding up against competition from supermarket websites with special Pesach sections, such as Tesco's.

"Supermarkets rely on loss-leaders to bring people in, but the proportion of offers on their shelves this year are ridiculously high.

"I question the viability of the supermarkets continuing with these Pesach ranges and the ethos behind it. If I offered their loss leaders, I know I would lose £3,000 on one Pesach line alone."

Purchasing Pesach items from Halpern's kosher store in Salford, Miriam Becker said she would be catering for large family gatherings, including children and grandchildren coming over from America.

"I have bought some products from the supermarkets. The deals are positive for us as customers, but I don't buy the staples there. The rest I buy from Halpern's because the range is much bigger."

Also shopping at Halpern's was young mother-of-one Tzirel Hiley, who runs a toy business. She voiced concern over the threat supermarket price-cutting posed to kosher shops.

"The retail world is going through major changes - especially with the increase in online retail - and high street shops are disappearing, bringing a lot of unemployment.

"I find it hard to understand why people go for the supermarket deals. How much are they really going to save? £20?

"We always use the kosher shops. We know the people - it's a sense of community."