* Case revives calls for change to euthanasia rules
* Doctor acquitted in second case of seven deaths
* Update to laws was electoral promise of Hollande (Adds acquittal of doctor in other case)
By Brian Love and Chine Labbé
PARIS, June 25 (Reuters) - The European Court of Human Rights has told France to maintain life support for a tetraplegic man who has spent nearly six years in a coma while it examines a last-ditch appeal by his parents.
The request from the rights court late on Tuesday came just hours after French judges ruled doctors should be allowed to end medical support that has kept Vincent Lambert artificially alive since a motorbike crash in September 2008.
Lambert's plight and another case where a court on Wednesday acquitted a doctor charged with accelerating the deaths of seven terminally ill patients by lethal injection is prompting calls for a revamp of France's ambiguous laws on euthanasia.
The court's request is set to delay by months or even years the outcome of a legal battle where Lambert's parents are resisting his wife Rachel's attempts to withdraw life support.
The Strasbourg-based court said in a statement the case would be treated "according to the fastest procedure possible". A spokesman there acknowledged that even emergency procedures can take months or up to one or two years.
Lambert, a former nurse in his late 30s, has been in a coma since his accident and is in a vegetative state. His medical team was set to turn off feeding and hydration equipment before his parents secured an injunction last January.
Few countries in the world explicitly permit euthanasia or assisted suicide, and Lambert's case has sparked renewed debate over President Francois Hollande's promise to revise France's rules on the issue.
A 2005 law on patient rights and care for the terminally ill leaves grey areas regarding more passive forms of euthanasia, stating that patient treatment should not involve "excessive obstination", according to government information services.
Jean Leonetti, the politician behind the existing rules who has been asked by Hollande to explore new legislative options, responded frostily on Wednesday to the news of yet more delays concerning Lambert's case.
"This is one appeal too far," he told France Inter radio.
In a separate case, a court in southwestern France acquitted a doctor sent to trial on charges that he accelerated the end for seven dying patients in 2010-11 by administering lethal injections.
Lawyers for doctor Nicolas Bonnemaison said their client's acquittal was a "monumental verdict" that, with the Lambert case, showed French political leaders should speed up changes to right-to-die rules.
"There's no hero or martyr here," said lawyer Benoit Ducos-Ader. "This will force politicians to move a bit faster."
As many as 25,000 people die a year in France after removal of medical support, according to Remi Keller, a member of the Council of State, the top administrative court that issued Tuesday's ruling.
On Wednesday in Britain, a paralysed car crash victim and the widow of a man who had locked-in-syndrome lost a legal bid at the country's highest court for the right to assisted suicide. (Additional reporting by Gilbert Reilhac and Claude Canellas; Editing by Mark John and Sonya Hepinstall)