SAAB is accused of attempting to influence a Swiss referendum that could determine whether or not the Swiss air force purchases 22 new JAS Gripen jets.
The aircraft-maker is accused of quietly funding campaigns in favor of the deal (worth $3.4 billion) by Swiss lawmakers.
Saab has neither confirmed nor denied the accusations, citing Swiss rules which "also include refraining from comment on campaign financing".
"We don't have any clear rules for referendum campaigns, as a result, foreign companies feel they can shamelessly get involved in national decisions," Swiss Social Democratic MP Evi Allemann told the TT news agency.
The developments come following a decision taken last week that a referendum on the deal would be held on May 18th. Opponents submitted over 100,000 signatures seeking a referendum, with campaigners hoping to block the Gripen deal, according to a report in The Local.
Under Switzerland's system of direct democracy, citizens can have the last word on a huge array of issues if campaigners muster enough signatures from voters in order to force a plebiscite. Polls have shown that a majority of voters oppose the Gripen deal, the report added.