Pressure is growing on government to act to protect construction workers against the risk of coronavirus.
Workers are still commuting to busy building sites despite the government crackdown on social distancing.
Housebuilding giant Taylor Wimpey is one of the few construction firms that has announced it is closing its sites to prevent the spread of Covid-19,
But Cabinet minister Michael Gove told the BBC building work could continue if it can be done safely in the open air.
Photos of workers crammed into tube trains and on crowded building sites have angered many.
Rival politicians, unions and workers themselves all warn that the work is non-essential and putting people’s health at risk.
Some projects have been shut. Transport for London said it will suspend work on the Crossrail scheme “unless they need to continue for operational safety reasons”.
But some construction workers have told the BBC other sites remain open with few safety measures to guard against coronavirus in place.
‘Everyone is very worried’
“Almost everything in the country has shut down or has begun to at least, apart from construction sites,” an architect, who asked to remain anonymous out of fear of losing their job, told the BBC.
“There is no other viable option to keep workers safe other than a lock-down. They’ve done it with pubs and clubs, and they should be doing the same here.”
One of the sites has thousands of people going in and out of it daily, the architect warned.
“Even though they have added hand sanitiser stations everywhere, people still have to use fingerprint scanners to gain access to the site when they go in or out which seemingly defeats the object of social distancing.
“Everyone is very worried.”
Housebuilder Redrow – whose current building work includes developments in South Wales, Manchester and London – said on Tuesday that its sites “currently remain open with strict precautions in place including enhanced levels of cleaning, additional hygiene facilities and social distancing”.