Ukrainian opposition leader Yulia Tymoshenko has been formally re-arrested on a fresh criminal charge, her lawyer said on Friday.

The move further complicates European Union efforts to secure Tymoshenko's release because she would stay in jail on this fresh charge even if her conviction for abuse of office, for which is serving a seven-year sentence, was overturned.

Unfortunately, the judge has announced an order under which Tymoshenko was arrested for a second time, Tymoshenko's party quoted lawyer Sergiy Vlasenko as saying on its web site

Vlasenko said the new arrest order was formally made in her cell in a Kiev police detention centre late on Thursday after a court hearing at her bedside.

Her family and supporters say the 51-year-old, who has been in police detention since mid-August, is suffering from back problems.

The second charge against Tymoshenko, a former prime minister, relates to alleged tax evasion and theft of government funds between 1996 and 2000 when she led the intermediary gas company Unified Energy Systems.

The abuse-of-office charge, for which was sentenced in October, relates to brokering a gas deal with Russia in 2009 when she was prime minister.

A leading light in the Orange Revolution protests in 2004 which overturned the old political order in the ex-Soviet republic, Tymoshenko says she is the victim of a vendetta by her political foe, President Viktor Yanukovich.

The EU says her trial is politically motivated. The fresh legal moves appear to confirm Yanukovich's unwillingness to heed Western calls for her release, and threaten the success of an EU-Ukraine summit in Kiev on December 19.

Agreements on political association and the creation of a free trade zone, mapping out a new strategic relationship between the bloc and Ukraine, are due to be initialled then.

(Writing By Richard Balmforth; editing by Robert Woodward)