The health minister, Stephen Ladyman, last night pledged big improvements in services to combat osteoporosis, the potentially crippling bone disease thought to affect up to one in three British women over 50.

The promise of a £20m injection to buy new scanners and provide extra staff in England came days before the prime minister is expected to declare an election.

The votes of women and elderly people are being eagerly chased by the three main parties, so the attempt to end the patchy provision of scanners to measure bone density could be politically useful.

Osteoporosis can often lead to falls, fractures and disability, but it can remain undiagnosed for a long time if the patient does not have an accident. Many older men also have the condition.

A recent survey by the National Osteoporosis Society suggested that 80 NHS hospitals in England lacked the necessary scanning equipment to measure bone density.

The machines, which costs between £31,000 and £97,000, costs a further £185,000 a year to staff and operate, and there has been some concern that those that are available are not used five days a week. Patients referred by GPs can wait up to 78 weeks for a scan. The average, according to the NOS, is 18 weeks.

Mr Ladyman said £3m this year should quickly increase the NHS's capacity to provide the diagnostic service. A further £17m spread over 2006-07 and 2007-8 should bring other improvements and cut waiting times.