KIEV, Aug 18 (Reuters) - Ukrainian President Viktor Yushchenko's office on Monday accused Prime Minister Yulia Tymoshenko, his "Orange Revolution" ally, of betraying national interests by not backing Georgia in its conflict with Russia.

Yushchenko, who has strongly supported Georgia, was swept into power by protests against electoral fraud after defeating a Moscow-backed rival in 2004. He then embarked on a pro-Western agenda, seeking membership of NATO and the European Union.

Yushchenko's deputy chief of staff accused Tymoshenko of remaining silent to secure Moscow's support during presidential elections in 2010.

"Russia's leaders are seriously considering supporting Prime Minister Yulia Tymoshenko in the presidential campaign once she ... fulfils the condition of adopting a passive position in the conflict with Georgia," Andriy Kyslynsky said in a comment on the presidential Web site.

Tymoshenko became Yushchenko's first prime minister but was sacked after seven months, only to become premier again last year when "orange" forces won a snap parliamentary election.

The president's office was handing prosecutors documents about Tymoshenko's "fully fledged work in the interests of the Russian side", the statement added.

"The public has a right to know how far politicians will go beyond the boundary where political battles end and the betrayal of national interests begins."

Kyslynsky provided no further evidence of his allegations.

Tymoshenko and her bloc have been careful to maintain a balanced position in the conflict over Georgia's breakaway region of South Ossetia, calling for an end to hostilities.

Yushchenko travelled to Tbilisi last week along with leaders of four central European states to show support for Georgian President Mikheil Saakashvili.

While avoiding criticism of the Kremlin, he enraged Moscow by placing restrictions on the movement of ships and aircraft from the Black Sea Fleet, based in Ukraine's Crimea peninsula.

Opinion polls give Tymoshenko 24 percent -- enough to win a presidential election if it were held now. Former Prime Minister Viktor Yanukovich, the rival Yushchenko beat in 2004, has just over 20 percent, while the president has about 7 percent.

(Writing by Ron Popeski, Editing by Meg Clothier)

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