Vienna prosecutors charged three people on Monday with helping to divert nearly 1 million euros ($1.3 million) from Telekom Austria to a right-wing political party.
The indictments are part of a sweeping probe into suspected corruption at the former monopoly, still partly state-owned.
Prosecutors said in a statement they had charged former company executive Rudolf Fischer, lobbyist Peter Hochegger, former politician Klaus Wittauer "and others" with breach of trust, falsifying testimony and money laundering.
Hochegger - who has denied any wrongdoing - did not immediately return a call to his office seeking comment, Wittauer could not be reached by phone and no contact details could be found for Fischer.
Last year, Hochegger admitted to a parliamentary committee investigating the affair that he had liberally spread money around the political world, but said the payments were legal.
Wittauer told the same committee he had not taken nor distributed money illegally.
Prosecutors cited 960,000 euros that Telekom Austria sent two advertising agencies working for the Alliance for the Future of Austria (BZO) "via fake invoices" before 2006 elections "without the knowledge of shareholders and without adequately getting something in return".
Hochegger, Wittauer and Fischer are also suspected of providing incorrect information to the parliamentary investigative panel looking into the matter, prosecutors said.
Joerg Haider, who died in 2008, split off the BZO from the right-wing Freedom Party in 2005. The BZO then replaced Freedom in a center-right coalition that governed until 2006 elections. It is now an opposition party under new leadership.
Prosecutors said they were still reviewing whether the payments might be linked to legislative changes that helped Telekom Austria at the time. They said they would try to get the BZO to return 940,000 euros of the money.
Current BZO leaders have distanced themselves from events in 2006. The party's deputy head said last week it would return the money in question should the defendants be convicted, and then try to get the money back via civil lawsuits.
The suspects have two weeks to appeal against the indictments. If convicted they face up to 10 years in jail.
Prosecutors are investigating suspected corruption at Telekom Austria by a total of about 40 individuals.
They brought their first charges against former top managers at Telekom Austria, including former deputy CEO Fischer, in October in a case of possible share price manipulation.
They said in November they were investigating Chief Executive Hannes Ametsreiter and other former company officials on suspicion of breach of trust. The company has dismissed the accusations against its CEO as "incomprehensible".
($1 = 0.7524 euros)
(Reporting by Michael Shields; Editing by Louise Ireland)