The number of people waiting for hospital treatment in England has hit a record high of 4.39 million, NHS figures show.
It comes amid an escalating row between the government and doctors over pensions.
Consultants have started refusing to do overtime shifts because they are being landed with large tax bills after changes to the way the pension system works.
The figures are fresh evidence of the impact on patients of the stand-off.
The total waiting for treatment in May is the highest since records began in 2007.
Around one in eight have been waiting longer than 18 weeks – the maximum length of time they should have to wait.