UBS , has hiked the salaries of some investment bankers to guard against staff poaching by competitors, Switzerland's largest bank said on Sunday.

There have been off-cycle salary increases at UBS Investment Bank to retain employees in critical positions, UBS spokesman Andreas Kern said, adding it was usual to adjust compensation to the market environment.

Earlier on Sunday Swiss paper Sonntag reported that hundreds of UBS managing directors at the investment bank, with salaries of around 270,000 Swiss francs ($243,200) on average, were receiving 50 percent higher wages to compensate for the loss of usual bonuses.

UBS, the world's largest wealth manager in terms of assets, declined to comment on the details of the article.

The bank is losing key staff in important areas to competitors and had to react, chairman Kaspar Villiger was reported as saying on Saturday.

Facing public anger over what many regarded as excessive bonuses, UBS undertook a radical overhaul of its executive pay system last year after its bet on risky U.S. assets backfired.

On Sunday, paper SonntagsZeitung reported the results of a poll that showed 75 percent of participants would vote in favor of government-imposed restrictions on management pay in Switzerland. Only 9 percent said they would vote against.

The poll of over 1,000 Swiss voters was carried out for Thomas Minder, a businessman heading a campaign against excessive management pay.

The campaign has already handed in a petition to the Federal government to force a national vote on the issue, which could take place in around a year's time but might have to wait until 2012.

(Reporting by Jason Rhodes)