Dhaka, Bangladesh (BBN)-Work to bring Bangladeshi factories used by north American retailers, including Walmart and Gap, up to fire and building safety standards will cost more than $150m (£87.9m) and take at least 18 months to complete.

In its first annual report, the US Alliance for Bangladeshi Worker Safety, formed in the wake of the Rana Plaza factory collapse in Dhaka in which more than 1,100 people died last April, said it had completed fire and building safety inspections of all the 587 factories its members now used, reports The Guardian.

Ten factories had been closed or partially closed, as a result of structural faults being revealed by inspections and members now used 600 factories against nearly 800 registered a year ago.

Ian Spaulding, a senior adviser to the Alliance, said: “People are realising that they can’t just buy from any factory.” Overall orders from Bangladesh had not been cut but consolidated among fewer suppliers.

The use of fewer suppliers is likely to cause unease in Bangladesh where factory owners fear they will lose business to rival countries as a result of the crackdown after the Rana Plaza disaster.

Alongside the Alliance, a 170-plus group of international retailers including Primark and Marks & Spencer are backing the Bangladesh Accord on Fire & Building Safety which is inspecting more than 1,500 clothing factories.

The Bangladesh government, backed by funds from the UK and The Netherlands is also inspecting thousands more garment production facilities.

Spaulding said that a key part of maintaining standards in Bangladesh’s clothing factories would be the introduction of democratic institutions, such as trade unions, that support workers rights and there remained some resistance from factory owners.

In April, it emerged that fewer than 300 of Bangladesh’s 5,000 clothing factories allowed trade unions.

BBN/JF-24July14-1:00pm (BST)