* Health shaping up as hot issue in next spring's election
* Rivals see Fillon reform plan as potential weakspot
* Conservative front-runner denies intent to privatise
By Richard Balmforth
PARIS, Dec 13 (Reuters) - Francois Fillon, tipped to win France's presidential election next year, sought on Tuesday to dispel fears over his plans to reform public healthcare as opponents accused him of backtracking and sowing confusion.
Fillon, 62, has raised concern even within his centre-right Les Republicains party with an election manifesto that foresees limiting public health insurance to serious or long-term illnesses, with everything else covered privately.
Signs that he favours a radical redrawing of a system largely unchanged since 1945, but which French citizens do not want to lose, have handed the opposition a stick to beat him with and suddenly made healthcare a hot-button election issue.
Though the system operates with debts of 110 billion euros ($117 billion), an opinion poll showed that 90 percent of people are opposed to cutting spending on public healthcare.
Aiming to counter criticism from political rivals and head off possible revolt in his own party on the way to the election next April and May, Fillon denied on Tuesday that he harboured plans to privatise parts of the health system.
"Instead of looking at the facts, my detractors suspect me of wanting to 'privatise' health insurance and cut down on spending there. This is quite clearly not true," he wrote in an article in Le Figaro, flagship newspaper of the centre-right.
The general public insurance now in force would continue to cover treatment as it does now, and people would actually be better reimbursed for glasses and dental care, he said.
Fillon's camp denied suggestions he was back-pedalling. But critics accused him of failing to clarify where he stood on his written manifesto pledge that only serious illnesses would be covered by the state.
"He is trying purely and simply to confuse the French," said Marisol Touraine, health minister in the Socialist government.
A spokesman for Fillon did little to help when asked whether common colds would qualify for state insurance cover or not.
"It depends on what kind of cold," the spokesman replied to France Inter public radio.
"He (Fillon) wants to calibrate reimbursement according to the level of sneezing," Touraine responded in a sarcastic tweet.
The far-right National Front (FN), whose leader Marine Le Pen is tipped in polls to face Fillon in the run-off vote next May, also weighed in.
"It's either deliberately fuzzy and he is hiding his real plan, which is to privatise the social security system ... or he is genuinely back-pedalling and that means we could, if Fillon is elected, be condemned to five years of immobility," said Florian Philippot, a leading FN official.
Fillon, a former prime minister, won his party's nomination with a programme in which he proposes slashing public spending by 100 billion euros, cutting half a million public sector jobs and extending the working week to 39 hours from 35.
But his healthcare plans have clearly worried people in his own party who fear he might squander the big lead he apparently holds over Le Pen.
Bernard Accoyer, secretary general of Les Republicains, has called for clarification, and Fillon was due to meet leading lights in the party later on Tuesday. (Additional reporting by Sophie Louet and Marine Pennetier; Writing by Richard Balmforth; Editing by Brian Love and Mark Trevelyan)