Patients are dying because of the SNP's free prescriptions policy, Scottish Conservative leader Ruth Davidson has said in her most outspoken intervention yet in the row over benefits.

Ms Davidson warned that money was being diverted away from other services including vital cancer drugs.

"People in Scotland are actively paying with their lives for this policy," she said.

However, the SNP accused her of "tasteless and inaccurate comments" for which she had not a "shred of evidence". The flagship policy has come under scrutiny in recent weeks since Labour warned it could not be right for rich people to get free prescriptions at the expense of other services. But the SNP says it has no plans to reintroduce charges, which it argues are a tax on the sick.

Ms Davidson said it was well known that Scotland had free prescriptions, but told Tory party members that what people did not know was "what it costs us".

She accused the SNP of presiding over a cut in thousands of nursing and midwifery posts and said that patients were missing out on cancer drugs because of the policy.

She pointed to the Tory-LibDem Coalition Government's Cancer Drugs Fund in England which provides expensive treatment to patients. A similar fund in Scotland would cost around £10 million, she said.

She added: "People in Scotland are actively paying with their lives for this policy. Because in England and Wales they have access to the cancer drugs fund, so people with rarer cancers can be treated for that, they can have lives extended.

"It may not make a difference to a huge number of people but to the people it makes a difference to, my God it makes a huge difference and we don't have that in Scotland."

Meanwhile, Ms Davidson admitted she might be part of the almost nine in 10 Scots households she warns receive more in public spending than they pay in taxes.

The Scottish Conservative leader said she did not know if she was one of the 12% of net contributors. But she refused to bow to SNP demands that she apologise for her comments.

Ms Davidson said she would "never make apology" for what she said was adding clarity to the debate on taxpayers' money. She admitted the 12% figure was "genuinely shocking". But she accused the SNP of criticising her without challenging the facts.

The SNP stepped up its call for Ms Davidson to apologise and accused her of counting pensioners and student among the 88%.

SNP MSP Kenneth Gibson added: "She appears to have counted all of the expenditure, but ignored most of the revenue – including corporation tax, business rates and North Sea oil revenues.

"So with a stroke of the pen, Ms Davidson has erased all of the wealth Scots generate when they go out to work in the morning."