Members of the Society of Radiographers (SoR) began a 24-hour walkout at 8am, in 37 trusts across England, over pay.
It will coincide with a second day of action by junior doctors and consultants in the British Medical Association (BMA), which has brought planned care in the NHS to a standstill.
The strike by radiographers is expected to significantly restrict access to key diagnostic tests and could lead to longer waits in A&E, hospital bosses warned.
Matthew Taylor, chief executive of the NHS Confederation, said: “Thousands of patients are at risk of not getting the scans and x-rays they need, this will include non-urgent activity such as some fracture clinics and GP walk ins also being cancelled and rebooked due to staff shortages with patients asked to come back for their x-ray on another day if it is not urgent.
“We know that these rearranged and cancelled appointments will contribute to the backlogs and could add further delays for elective recovery and could also potentially increase waits in emergency departments and increase length of stay in hospital.”
Consultants, junior doctors and radiographers will hold a rally from 1pm on Tuesday near Manchester Central, where the Conservative Party conference is taking place.
Leandre Archer, head of industrial relations at the SoR, is expected to say that radiographers are “struggling to make ends meet while the cost of living soars” and cannot afford childcare.
“They work excessive hours to deal with increasing vacancies. They watch colleagues leaving the NHS, seeking better work and better pay,” she will say.
The SoR claims it has seen a 32 per cent real-terms fall in income since 2008, with staff shortages causing burnout.
It came as consultants from the BMA offered to call off strikes for four weeks if ministers agree to talks through the conciliation service Acas.
Dr Vishal Sharma, chair of the BMA consultants committee, has written to the Prime Minister offering to enter negotiations, with Acas facilitating these talks “if necessary”.
But the letter states that if medics do not receive a “credible deal we can put to our members” by November 3, then strike dates will be set for November and December.
Sir Julian Hartley, chief executive of NHS Providers, said: “Trust leaders hope this olive branch from consultants to the Government could be a first step to ending disruptive strikes.
“Something has to give. We can’t go into another ‘full on’ winter with the threat of more strikes hanging over the NHS.
“We have said before that we would welcome all sides using an intermediary like Acas if that helps to break the deadlock.”