Average waiting times for inpatients were 41 days in 1997 but by last year reached 49 days, according to NHS figures. Spending has more than doubled to £90 billion in the same time period.

The figures measure the time from date of diagnosis to date of admission.

Opposition politicians said the statistics showed targets were undermining patient care.

Shadow Health Secretary Andrew Lansley said: "This shows how the bigger picture gets neglected in order to meet the Government's top-down targets.

"Patients get a worse deal overall. Labour has to accept that their obsession with bureaucracy and running the NHS around a few targets does not have the best outcome for patients. In meeting one target, another patient misses out. It is simply unfair."

Liberal Democrat health spokesman Norman Lamb said: "These figures massively undermine Labour's claims to have made a substantial difference to NHS waiting times.

"There is a danger if you focus solely on the longest waiting times that clinical priorities get distorted."

Since 1997, ministers have focused on eliminating the longest waits. Before then, waits of 18 months were not uncommon, but now no-one waits longer than six months.

Many of the big reductions in treatment time have been for minor operations such as cataracts, while for some cancers average waiting times have increased, the figures show.