Construction workers gather at Tower Hill on Sunday for a rally and to lay wreaths, hold a minute’s silence and release black balloons in memory of those killed on building sites.

Jobs on building sites are described by safety campaigners as “the most dangerous work in Britain”, with 49 workers killed in 2011-12 and thousands more seriously injured.

“This is the day workers come together to remember friends and workmates who have been killed or injured at work,” said the UCATT construction union’s London region secretary Jerry Swain. “It is also to state our determination to ensure safe working conditions.”

He is to address the 11am rally together with the Construction Safety campaign’s Tony O’Brien, next to the Building Worker memorial statue opposite the Tower of London.

Four workers were killed in London alone in 2011-12 and another eight in the previous 12 months.

The union fears safety is being undermined, with regulations on head protection and the Tower Cranes register being scrapped earlier this month.

“The government is slashing regulations in the name of ‘freeing up’ business and cutting red tape,” the union chief added. “This is placing workers in danger and will lead to a rise in deaths and injury.”

The Health & Safety Executive’s budget is being cut by 35 per cent by 2015, the union points out. Rules exempting many self-employed workers from safety laws are also being brought in, with proposals to relax the requirement for employment agencies to take responsibility for their workers’ safety.