* Collection worth over 35 mln euros, comes from failed bank
* Opponents say government broke rules on art classification
* Petition against sale gathered over 9,000 signatures
LISBON, Feb 4 (Reuters) - A Portuguese court threw out objections by opposition lawmakers, prosecutors and the public to an auction of 85 paintings by Catalan artist Joan Miro owned by the indebted nation, allowing the sale to start in London later on Tuesday.
The Miro collection, estimated to be worth a total of more than 35 million euros ($47 million), became state property after Portugal nationalised the failed bank BPN in 2008.
The paintings are being offered by state holding company Parvalorem, with the government's consent.
Parvalorem is in charge of minimising the impact of BPN's old debts and bad loans on public accounts, even after it was sold off for around 40 million euros as Portugal grapples with its debt and economic crisis.
The most highly valued piece in the collection, "Femmes et oiseaux (Women and Birds)" dating from 1968, is expected to fetch between 4.8 million euros and 8.3 million euros.
More than 9,200 people have signed an online petition calling for the collection to be kept in Portugal, despite the drastic austerity measures imposed over the past three years under an international bailout.
The hearing, involving opponents of the sale and representatives of the government, continued late into the night on Monday but eventually went the way of the government.
"The appeal to suspend the auction was denied," an official at the Lisbon Administrative Court said after opposition lawmakers argued that the centre-right government had violated rules on the classification of cultural assets.
The appeal, which also accused the administration of ignoring "the immeasurable immaterial value" of the collection to Portugal, had been backed by the public prosecutor's office.
Socialist member of parliament Gabriela Canavilhas, one of the authors of the appeal, said the opponents of the sale would analyse the details of the court's ruling to decide how to proceed. She did not rule out a new appeal.
The two-day sale, The Art of the Surreal and Impressionist/Modern, by auction house Christie's and involving other artists starts at 1900 GMT and will continue on Wednesday. ($1 = 0.7397 euros) (Reporting by Andrei Khalip, Editing by Axel Bugge and Alison Williams)