Prosecutors portray Trump's ex-campaign chief as a liar and tax cheat

* First trial test in special counsel's inquiry on Russia meddling

* Ex-Trump aide Manafort hid millions in offshore accounts -prosecutors

* Manafort's lawyers attack star government witness Rick Gates (Adds details of Devine's testimony, comments from prosecutors)

By Nathan Layne, Sarah N. Lynch and Karen Freifeld

ALEXANDRIA, Va., July 31 (Reuters) - Prosecutors portrayed U.S. President Donald Trump's onetime campaign chairman Paul Manafort as a tax cheat who used offshore accounts to hide tens of millions of dollars from political work in Ukraine, as the first trial from a probe into Russia's meddling in the 2016 election got off to a quick start on Tuesday.

Manafort lived an extravagant lifestyle, snapping up expensive homes and cars, and spending more than half a million dollars on "fancy clothes" and $21,000 for a watch, a prosecutor said in the government's opening statement at the trial in a Virginia federal court.

"A man in this courtroom believed the law did not apply to him. Not tax, not banking law," said Uzo Asonye, a member of Special Counsel Robert Mueller's team looking at possible collusion between Russia and the Trump campaign in 2016.

In describing the 18 counts facing Manafort, Asonye said that Manafort did not pay taxes on a large portion of the $60 million he earned working for pro-Russian politicians in Ukraine, hid the income in a web of 30 overseas bank accounts, and lied to U.S. banks to borrow millions of dollars against his real estate holdings once the money from Ukraine dried up.

"All of these charges boil down to one simple issue: that Paul Manafort lied," Asonye said.

Manafort's attorney Thomas Zehnle painted a drastically different portrait of Manafort, calling him a successful political consultant of 40 years who left the day-to-day operations of his company to his former associate Rick Gates, who betrayed him.

Zehnle made it clear that attacking the credibility of Gates, who pleaded guilty in February and agreed to cooperate with Mueller's investigation, would be a central plank of the defense.

Gates is expected to be a star witness at the trial.

"Rick Gates had his hand in the cookie jar," Zehnle said, claiming that Gates was not truthful with the accountants who prepared Manafort's tax returns and kept his name on offshore accounts to conceal an embezzlement scheme.

Thomas Green, who represents Gates, did not respond to a request for comment on the new accusations.

The government also presented its first witness, Tad Devine, a political consultant who recalled his work with Manafort in Ukraine to help pro-Russian political figure Viktor Yanukovych, who was swept from power and fled to Russia in 2014.