GMB Union bosses have sent a letter to Asda chair Allan Leighton accusing the supermarket of “penny-pinching” tactics causing worker conditions to fall behind those of its rivals.

The move comes after the union claimed the retailer’s store staff were among the lowest-paid supermarket workers in the UK last week, despite their latest pay increase.

In her letter to Leighton, seen by The Grocer, GMB Union national officer Nadine Houghton said: “Shop floor colleagues are the backbone of Asda’s recovery and GMB believes you have a deep understanding of just how fundamental they are to Asda’s turnaround.

“Whilst there is nothing illegal in how Asda has approached pay, we would argue it has certainly been immoral,” she continued.

GMB claimed that the grocery specialist had decided not to raise salaries at Asda at the last moment and condemned its March announcement of a staggered pay increase.

The supermarket’s base retail pay reached £12.45 an hour on 6 July and is set to jump to £12.60 an hour by October. Despite this, GMB says rivals are already offering their staff more, such as Tesco (£12.64 an hour) and Sainsbury’s (£12.60 an hour).

Houghton added: “It all adds up and our members view is pennies are being pinched from their pockets at a time when Asda needs everyone to pull together.”

The trade union urged the retailer to agree to an immediate increase, to backdate pay rises to April, and commit to yearly pay reviews with the union.

Asda highlighted that it was not the only grocer to phase in pay increases, with Tesco’s pay rising to £12.64 at the end of August and Sainsbury’s salaries jumping to £12.60 at the start of August.

Additionally, the company noted that it had boosted hourly staff pay by 4.7% this year, marking an above-inflation increase on a par with its competitors.

Asda denied that it had left its minimum wage change to the last possible moment, insisting that the move had coincided with its pay cycle.

An Asda spokesperson said: “Earlier this year, we announced an £80m investment in retail pay, with rates rising from £12.04 in April to £12.60 in October.

“This phased approach ensures we can continue to offer competitive rates and is similar to the approach taken by other major supermarkets.

“Asda has invested £500 million in retail pay since 2021, as well as introducing a range of enhanced benefits — including 15% colleague discount and enhanced maternity, paternity, and kinship leave policies — reinforcing our commitment to supporting colleagues both in and outside the workplace.”

The letter follows Asda recently revealing plans to overhaul its store management structure, which will see key leadership roles merged in an effort to simplify its business.

Earlier this week, the supermarket’s managers depot management team also geared up to vote on whether GMB would become its official union representative, following a landmark decision by the Central Arbitration Committee (CAC).

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