The number of people waiting for a hospital operation in England is at its highest for more than a decade
An estimated 4.2m people are waiting to be seen – the highest since 2007.
April's figures also showed growing numbers waiting more than 18 weeks, the treatment target time, including people due to have cataract or back surgery and knee and hip replacements.
The rising numbers come after the health service was forced to postpone thousands of operations in the winter.
That action was taken to relieve the pressure on A&E departments.
It means the number of patients now waiting longer than they should has topped 500,000 for the first time since 2008, although some trusts have had problems reporting data in previous months which has kept the figures lower than they were in reality.
Patients 'paying the price'
Janet Davies, Royal College of Nursing general secretary, said: "Cancelling non-urgent care may have helped the NHS fight though one of the worst winters in recent memory, but patients in need of elective surgery should not have to pay the price for chronic staff shortages and years of underfunding."
Phillippa Hentsch, of NHS Providers, which represents hospitals, said the rising numbers were "worrying".
She also highlighted the continued missed targets in cancer and A&E.
And she added they demonstrated the need for "substantial" resources to be announced in the long-term funding settlement that has been promised by Prime Minister Theresa May.
Ministers are currently discussing how much the NHS should get, with an announcement expected in the next few weeks in time for the 70th anniversary of the creation of the health service at the start of July.