The retailer first ran the Families and Friends promotion in February and it is expected to lift sales at M&S ahead of its first-quarter update in July.
More than 70,000 staff have been given a dozen vouchers, offering 20 per cent off clothing, food and homewares, according to the Daily Telegraph.
The vouchers are valid between next Thursday and Saturday. M&S’s first quarter finishes at the end of June. The retailer is also promoting its champagne and wine and offering a third off its furniture.