Morning Noon & Night marketing director Stephen Thompson said the deal, which ends a 13-year relationship with Aberness, had been in the pipeline for months.
But Somerfield said it had been unaware Scottish Mace wholesaler Aberness was about to lose the Morning Noon & Night account when it bought the company last month.
A spokesman said: “We looked at all possibilities when we decided to buy Aberness.
“It is regrettable that MN&N no longer wishes to be a part of the successful Mace business, but it is still a very good deal.”
Morning Noon & Night, which has 50 stores and is ranked 24 in The Grocer Top 50, sourced 45% of its stock from Aberness, but had already become Filshill’s
biggest customer - sourcing £8m worth of alcohol through it a year. Key Lekkerland and Sugro member Filshill has now taken over all grocery, tobacco, soft drinks, confectionery, snacks and household lines from Aberness.
Thompson said Filshill had been able to offer a better deal than Aberness as it could deliver to all stores every day if required, as opposed to Aberness’ two to three deliveries a week. MN&N will carry on using a variety of other suppliers including Kerry Foods and Fife Creamery for the rest of its stock, he added.
Filshill managing director Ronnie Hannah said that he had been “trying for years” to persuade Morning Noon & Night to transfer its business.
The Morning Noon & Night coup was just the first of three announcements it was set to make as it expanded operations in Scotland, he added.
An additional 15,000 sq ft had been added to the 170,000 sq ft Filshill depot so it could carry the volume of stock required to cater for peaks in demand when servicing MN&N, he added. Extra deliveries to MN&N had already started this week, he said.
Filshill already delivered alcohol to stores two or three times a week, but would now visit three or four times a week, in line with MN&N’s demands.
Hannah confirmed: “This deal was arranged before Somerfield came into it.”