Data published by NHS England shows 0.9 million attendances were recorded in April 2020, down 57% from 2.1 million in April 2019.
The number is the lowest for any calendar month since current records began in August 2010.
NHS England, which published the figures, said the fall was "likely to be a result of the Covid-19 response" - an indication that people have been staying away from A&E departments because of the coronavirus outbreak.
Emergency admissions to A&E departments at hospitals in England also showed a sharp fall last month, down 39% from 535,226 in April 2019 to 326,581 in April 2020.
Number of attendances recorded in April 2020 Source: NHS England
NHS England again said this was likely to be a consequence of the coronavirus outbreak.
Data also shows the number of patients waiting to start treatment at the end of March was 4.2 million, down on the 4.4 million in the previous month which could be due to the fact the UK lockdown was announced on March 23.
Pete Sharp, 60, died on April 27 following a lung cancer diagnosis in January.
His youngest daughter said Mr Sharp was heartbroken after the chance for more time with his family was “snapped away from him” due to the outbreak.
Tayler Sharp, 23, said her father was diagnosed with stage four lung cancer which had spread to his lymph nodes.
She said: "It was just kind of downhill from there, he said he felt like a ping pong ball because he was going from appointment to appointment."
Miss Sharp said the surgery scheduled for March 30 may have given Mr Sharp more time with his family.
However, the week before he was due to have the surgery Mr Sharp, from Kettering, was told it was not safe for him to have it due to the pandemic.
"He had been given a 98% chance of pulling through the operation and living for however long, and it was just snapped away from him just like that because of coronavirus. It was awful," she added.
The latest A&E figures come as health leaders have warned it will be months before the NHS is able to fully restart services in the wake of the Covid-19 pandemic.
Experts from the Health Foundation, the King’s Fund and the Nuffield Trust will tell MPs on Thursday of the significant challenges facing the health service as it tries to create a "new normal".
In a joint submission to the Commons Health and Social Care Committee, the Health Foundation, the King’s Fund and Nuffield Trust said the Government and health and care leaders should not underestimate the pandemic’s impact on already exhausted staff.
They warned that an information campaign will be needed to urge the public to overcome their fears and start using the NHS again, while preparations must also be made for a possible second peak of Covid-19 alongside the usual winter pressures such as seasonal flu.
The groups warned that the pandemic has exposed "pre-existing weaknesses", most obviously a long-term under-investment in health and care services and a “precarious” social care system.
"These issues will still need to be tackled alongside the backlog of demand," they said.