Tackling the waits patients have to endure before they get basic scans are a new Liberal Democrat priority, Charles Kennedy has said.
Too many patients face agonising waits, says Mr Kennedy
Mr Kennedy put the battle against "hidden" waiting lists at the forefront in a speech on his NHS plans.
Research by his party suggests people are waiting six months or more for routine scans to detect tumours, cancers and heart conditions.
The Lib Dem leader also wants to remove centrally imposed targets.
Few of the policies in the speech, delivered in Westminster, are new but Mr Kennedy says healthcare is a top campaigning topic and wants to spread his message.
Last November, ministers hailed the lowest NHS waiting lists in 40 years.
But Mr Kennedy says it is a scandal the government does not bother to collect figures on people waiting after being referred by their GPs for diagnostic tests.
"Put yourself in the place of one of those patients," he said.
"Your GP has decided you may have a serious, perhaps life-threatening, condition.
"But if you can't afford to go private - six months - a year later - you are still waiting to find out what is wrong - which means no treatment has started."
Mr Kennedy says a Lib Dem government would make the issue a very high priority.
It would collect the "hidden" waiting times and introduce schemes to make best use of equipment, recruit diagnostic staff and invest in infrastructure.
Mr Kennedy linked the problem to the way Whitehall-imposed targets meant other issues went to the back of the queue, he said.
He accused ministers of mistrusting doctors and nurses on the frontline.
"Despite all the spin and the 'New Labour' branding, this administration is 'Old Labour' in its instinctive statism," he said.
"It cannot resist micro-managing how local hospitals and GP surgeries are run."
Mr Kennedy said he would help ensure more decisions are taken locally by making government relinquish its target-setting role.
It would also abolish the strategic health authorities and reduce the number of arms-length bodies which inspect and monitor NHS work.
Mr Kennedy also used the speech to attack the Conservative and Labour focus on providing "choice" on health - instead the key was providing quality care locally.
Health Secretary John Reid said Mr Kennedy had identified the right priorities but would fail patients by siding with "producers" - the professionals.
"Tough targets have helped turn around accident and emergency where 19 out of 20 people are now seen, diagnosed and treated within four hours," he said.
"And patient choice - a concept the Liberals reject - will empower patients to get the type of treatment they want in the future."
Tory health spokesman Andrew Lansley claimed the Lib Dems' policies could produce bureaucracy and £15bn in cuts in three years.
"The Liberal Democrats don't believe in patient choice although it will be a key driver of higher standards of healthcare in the NHS," he added.