The number of NHS staff vacancies has increased and researchers have warned the growing nurse shortages "risk becoming a national emergency."
There were 107,743 vacancies in England at the end of June, up from 98,475 in March and bucking a downward trend seen in 2017/18, a quarterly report revealed.
Trusts across England were £814 million in deficit at the end of June.
Independent think tank The King’s Fund said growing nurse shortages are "symptomatic of a long-term failure in workforce planning".
Siva Anandaciva, chief analyst at The King’s Fund, said the "Report shows that the NHS is heading for another tough winter.
"Widespread and Growing nursing shortages now risk becoming a national emergency and are symptomatic of a long-term failure in workforce planning, which has been exacerbated by the impact of Brexit and short-sighted immigration policies," Anandaciva added.
NHS Improvement said the rise, the result of increasing demand and high leaving rates, is forecast to continue throughout the financial year.
Around 1.1 million full-time staff are currently employed by the NHS, the figures from NHS Improvement show.
Between April and June, NHS trusts spent £805 million on bank staff, £102 million more than planned, and an additional £599 million on agency staff, which was £32 million over-budget, according to the report.
NHS Improvement said this is £22 million better than planned at the beginning of the year, but £78 million worse than the year ending June 2017.
The projected deficit for the end of 2018/19, which stands at £519 million, is “clearly unaffordable”, the report said.
A&E staff saw 5,602,531 patients in less than four hours between April and June, compared to 5,427,860 in the same period last year, despite a rise in attendance, the figures show.
However, 3,402 patients were waiting longer than 52 weeks for elective treatment in June, compared to 1,475 at the same time last year.
Chris Hopson, chief executive of NHS Providers, said the "Trusts are doing all they can to respond to a rapidly increasing demand, growing workforce and shortages and continuing pressure on NHS finances."
"Trusts tell us they are most worried about the workforce shortages they face, and it’s a real concern that these figures have shown such a big increase in vacancy levels.
"It’s worrying that this problem is getting worse rather than better."
Ian Dalton, chief executive of NHS Improvement, said: “Staff are working extremely hard to cope with a rise in A&E attendances and high occupancy levels.
"We are helping trusts ensure that no-one stays in hospital longer than they need to, so that beds are free for other patients who urgently need them."