Mounting pressure on hospital waiting lists in England has left the NHS "creaking at the seams", doctors say.
Overall, the health service is still hitting its 18-week deadline, but performance is dropping in some areas.
The official NHS data for May showed more people were waiting over 18 weeks than in May 2010 when the coalition was formed.
Doctors' leaders described the trend as worrying, but ministers insisted waiting times were under control.
The figures come as a survey by the independent think tank the King's Fund suggests a quarter of NHS finance directors in England think the cuts they are making will affect patient care.
The NHS has been told it should see 90% of in-patients within 18 weeks - the 10% leeway is allowed to reflect the fact that some patients may wait longer for valid personal or medical reasons.
This expectation was reiterated last month when David Cameron personally promised the standard would be kept in an attempt to calm fears about the government's controversial NHS reform programme.
The latest data showed that 90.8% of the 300,000 patients seen in May were within the timeframe, but this is down from 92.9% in the same month last year.
What is more, the national figures mask the pressure building behind the scenes.
About a third of the country is not meeting the 90% target with the national figure only propped up by other places that are over-performing.
Certain specialities are also facing particular difficulties. In orthopaedics, which is the most common area of non-emergency care and includes operations such as hip and knee replacements, nearly one in seven patients waited longer than 18 weeks.
There are also a growing number of patients facing longer waits - as the BBC revealed earlier this week.
Of the 2.5m still waiting for treatment, there are nearly 225,000 people who have waited over 18 weeks for treatment - up by 8% on a year ago, these latest figures show.
The increasing pressure has been put down to a combination of rising demand and cost-saving measures by trusts, such as cuts to the amount of overtime that is available.
Sir Richard Thompson, president of the Royal College of Physicians, said: "The apparent rise in waiting lists is both worrying for patients and evidence of an underlying cause - the increasing pressures on the NHS in general.
"The NHS is now creaking at the seams. Our members are finding it difficult to cope."
And shadow health secretary John Healey added: "The NHS is starting to go backwards again under the Tories."
But Health Secretary Andrew Lansley said waiting times were a priority for the government and still remained "low and stable".
He added: "This is against a backdrop of rising demand for NHS services, so the low waiting times are a testimony to the hard work of NHS staff."
The the latest King's Fund survey of NHS finance directors found almost half of the 29 respondents need to make efficiency savings of 6% or more this year.
Half of those said they were "uncertain" that they could achieve this, and around a quarter warned it could not be done without harming patient care.
Responding to the survey. Health Minister Simon Burns said managers should be able to deliver savings through working more efficiently.