Decisions on which shops reopen after lockdown should be based on safety, not their size or business type, the British Retail Consortium has said.

Chief executive Helen Dickinson told the BBC she expects a “gradual lifting” of the restrictions with schools and transport reopening early on.

Ms Dickinson said it would be harder for retail staff to return to work while schools remain closed.

Boris Johnson will address the nation about the restrictions later on Sunday.

The prime minister is not expected to provide dates for when the coronavirus restrictions – first announced on 23 March – might change.

But a senior government source has told the BBC that garden centres in England will be allowed to reopen from Wednesday provided they comply with social distancing.

Mr Johnson is expected to confirm this on Sunday, when he is also set to unveil a new Covid-19 alert system in England to track the virus.

Meanwhile, Ms Dickinson believes the government’s guidance will reflect her organisation’s own advice on the practical measures that can be taken to promote staff and customer safety.

These measures would include staggering shift times, managing the number of people in store, and the use of plastic screens at payment points.

She said it is “incumbent” on retailers to ensure they can operate safely otherwise “they shouldn’t open”, adding that supermarkets have “shown us the way” over the past couple of months.

Safety measures, she added, would “give us confidence as shoppers, members of the public, that we can go out to shop”.

She said a phased lifting of restrictions across different industries, with schools and transport addressed early on would help those retail staff with children.

In a letter to the Observer, the head of the shop workers’ union, Usdaw, and three other major union leaders, said they will not recommend their members return to work unless the government guarantees “the right policies and practices are in place to make workplaces safe”.

“The trade union movement wants to be able to recommend the government’s back-to-work plans,” the letter said.

“But for us to do that we need to ensure that ministers have listened and that we stay safe and save lives at work too.”

Workers could also face issues getting to work. On Saturday, Transport Secretary Grant Shapps said even with public transport reverting to a full service, social distancing measures would leave effective capacity for only one in 10 passengers in many parts of the network.

He urged people returning to work to walk or cycle, and announced pop-up bike lanes, wider pavements, safer junctions, and cycle and bus-only corridors will be created in England within weeks as part of a £250m emergency fund.

Ms Dickinson also urged the government to ensure we avoid “a cliff edge of support falling way as soon as restrictions lifted”.

She called for “some form of tapering down” of the government’s job retention scheme, which is set to run until the end of June.