Details of factories used by the brands, including Primark and H&M, will be collected by next Monday and an initial inspection programme to identify grave hazards and the need for urgent repairs completed in nine months.
In the meantime any immediate threats identified by other inspections or workers will result in factories being shut down though employees will continue to be paid, according to the accord.
The contract has been agreed between retailers, international and local trade unions and non-governmental organisations. It was put in place after the collapse of the eight-storey Rana Plaza building in April, a catastrophe that focused world attention on safety standards at Bangladesh's garment export industry, which supplies clothes for some of the world's best-known retailers.
Primark has announced compensation for victims and their families. Some of those injured and killed in the incident in Dhaka worked for a company that supplied the brand.
"These will focus on those issues that pose grave and immediate risks to workers, in particular inadequate emergency infrastructure and procedures (eg fire exits, fire training and evacuation) and fundamental flaws that could lead to a partial or total structural failure of a factory building," said the committee overseeing the programme.
"In the interim period, while details are being finalised and the inspectorate is being built, an emergency protocol will ensure swift action to protect workers at any factory where existing inspection programmes or worker reports identify an immediate threat to life and limb."
In such cases, signatory companies will be notified and factory owners ordered to shut down operations pending investigation and repair, while workers will be informed of potential dangers and their right to refuse to enter a potentially unsafe building.
Justine Greening, the International Development Secretary, welcomed the move, saying the Rana Plaza collapse "was a wake-up call about the urgent need to improve safety standards for employees in developing countries". She said the UK Government was working with Bangladeshi authorities to offer technical support and advice on standards but that UK retailers also had a role to play.