Only five of the 27 global clothing brands linked to the Bangladesh factory that collapsed last year with the loss of 1,138 lives have committed to paying into a compensation fund for the victims.

The Clean Clothes Campaign, which wants improved conditions in the industry, said only Zara-owner Inditex, Mango, Canada's Loblaw, Denmark's Mascot and El Corte of Spain had committed to the fund, which is trying to raise $40m in time for the anniversary of the Rana Plaza factory disaster in April.

Several big British brands, including Primark and Matalan, are among the companies that have not paid into the fund, although Primark has paid the wages of workers laid off after the disaster. Other big brands connected to the factory include Walmart, Benetton and JC Penney. The collapse, the deadliest disaster in the history of the clothes industry, also left more than 2,000 injured.

The CCC campaign, which is supported by the International Labour Organisation (ILO), said it was "time for clothing brands to pay up".Global trade unions urged consumers to bombard their favourite brands with demands that they pay into the fund. "It is time to name, shame and campaign," said Monika Kemperle, assistant general secretary global trade union body IndustriALL. "On April 24, one year will have passed since the horror of Rana Plaza. No more excuses."

Frances O'Grady, general secretary of the TUC, wrote to Alessandro Benetton, the chairman of the fashion chain and heir to the family's $2bn fortune, to demand the Italian company pays into the fund.

"Nothing can be done to bring back those killed, or to reverse the psychological and physical scars that survivors will carry with them for the rest of their lives," she said. "However something can and should be done to alleviate the financial and health impacts."

O'Grady said Benetton's donation should "reflect the size of your company and take into account the direct relationship your company had with at least one of the factories in the building".

Ineke Zeldenrust of the CCC said: "Compensation efforts to date have been completely haphazard, unequal, unpredictable and non-transparent, and have left large groups of victims with nothing."

A spokesman for Primark, which is owned by Associated British Foods (ABF), which played a leading role in the immediate aftermath of the crisis, said it had "already paid short-term financial aid to all the employees at Rana Plaza, most of whom were making clothes for its competitors … and remains committed to paying long-term compensation to the workers employed by its supplier in the Rana Plaza building."