Nearly 50 percent of Vietnamese companies admit to bribing officials in order to bid on contracts, a new survey shows, but experts say the real figure could be far higher.

About 80 percent of businesses in the communist country reported that corruption had hurt their operations, according to a Vietnam Chamber of Commerce and Industry (VCCI) survey released Wednesday.

Nearly 50 percent of respondents said they had to pay bribes -- often in the form of cash, expensive gifts or luxury holidays -- to officials in order to bid on contracts to provide items or services to the public sector.

"The true picture of corruption might even be more serious than these figures suggest," said Le Dang Doanh, a senior economist and former government adviser.

The survey reflected "just a part of a painful truth that Vietnamese companies are suffering now -- they are facing many difficulties," he told AFP.

"State officials must be supervised in an open, transparent and independent manner. These officials have relied too much on their personal relationships in the handling of business," he said.

"The corruption issue is not yet settled and (this survey) sends that warning signal to the authorities. Administrative reforms should be more real and effective."

The survey interviewed 270 businesses and a cross section of entrepreneurs, business associations and civil servants across Vietnam.

Some 63 percent of firms interviewed said the business licensing system was complicated and unclear, and was a key driver of corruption.

Conrad Zellmann, of the non-government Towards Transparency organisation, said the survey was a "timely effort" to raise awareness of the role of business in addressing corruption as Vietnam works to meet its commitments under UN anti-corruption conventions.

At a national conference earlier this year, the communist party discussed ways to tackle graft and rising inequality, which officials said posed the "biggest risks to the ruling party."