ZURICH, Dec 20 (Reuters) - Switzerland's centre-left Social Democrats launched a referendum campaign on Friday to halt government plans to spend 6 billion Swiss francs ($6.1 billion) on replacing the neutral country's ageing fleet of fighter jets.
By gathering enough voter signatures, the party - a member of the coalition government - could force a binding referendum on the issue under the Swiss system of direct democracy.
"Switzerland does not need luxury fighter jets that cost 6 billion francs," the party said, saying cheaper aircraft could also do the job of training pilots and policing Swiss airspace.
The government in May split off its purchase of new fighter jets from its order of new surface-to-air defences.
Switzerland had previously agreed to spend up to 8 billion francs for a combined package under its Air2030 programme, but divided the plan so that voters could decide separately on buying new jets in a likely referendum.
European aerospace group Airbus, France's Dassault , Sweden's Saab, and Boeing and Lockheed Martin from the United States submitted bids in January. Swiss authorities later excluded Saab from the race, saying its entry was not far enough along to compete properly.
Switzerland's stable of Boeing McDonnell Douglas F/A-18C and D Hornets and Northrop F-5 Tigers is scheduled to be retired within years. Airbus's Eurofighter, Boeing's F/A-18 Super Hornet, Dassault's Rafale, and F-35As made by Lockheed Martin are in the running.
New jets are to be delivered by 2025.
Switzerland, which last fought a short war in 1847, has struggled in the past to persuade citizens to back a deal for new fighters. In 2014, around 52% voted against a 3.5 billion franc plan to buy 22 Gripen fighter jets from Saab.
$1 = 0.9803 Swiss francs Reporting by Michael Shields Editing by Frances Kerry