Tory plans for the NHS would do more damage than good, the health secretary has claimed.

Declaring health to be the big issue of the next general election, John Reid argued that the proposal for vouchers to cover 60 per cent of the cost of a private operation would give patients an "exit visa" from the health service at the expense of those who couldn't afford to pay.

Although he conceded that more work was needed, he accused the Conservative Party of "giving up on one of the most popular institutions in the country".

"They have given up on the values of the National Health Service itself," he said.

"That will be the choice for the people at the next general election."

"It is a choice between an NHS based on need, not ability, to pay with Labour, or a privatised health scheme based on ability to pay, not need, under the Tories."

His comments follow a speech by foreign secretary Jack Straw, in which he criticised the Conservatives policy over Europe and the European single currency.

Reid, who replaced Alan Milburn at the Department of Health during the last reshuffle, argued that the cost of a private operation is higher than that on the NHS, leaving patients with larger bills.

The plans were "more extreme than anything Mrs Thatcher ever thought possible; capable of unleashing more damage on the NHS than all the previous Conservative governments put together," he said.

"That is why I believe the future of health provision in this country will be the dividing line at the next general election."

The Conservatives dismissed the criticism.

"The Conservative Party firmly believes in the principles of the National Health Service," said shadow health minister Simon Burns.

"Under a Conservative administration the NHS will offer high quality care, free at the point of use and irrespective of ability to pay.

"It is extraordinarily cheap politics for John Reid to deliberately misrepresent Conservative intentions for party political gain. His comments have no basis in truth.

"Britain currently has a two-tier health system. Choice of hospital treatment is only available to people who pay their taxes and then pay again for private healthcare.

"The rest have no choice. Our patient's passport will make choice universal - extending it to all patients, not just those who can pay."