Vietnam's ruling Communist Party has pledged to wipe out corruption in its ranks amid a public outcry over a top-level scandal.
Nong Duc Manh called for cadres 'with good moral quality'
General Secretary Nong Duc Manh warned party members the issue was threatening "the survival of our regime".
He was speaking at the opening of the 10th party congress, which will also consider possible leadership changes.
Senior transport ministry officials are accused of using state funds to bet on football matches and buy luxury cars.
Transport Minister Dao Dinh Binh resigned over the issue earlier this month.
Mr Manh told the congress that "intensifying the fight" against corruption and wastefulness was "the pressing requirement by the society and the political determination of our party".
He stressed the party aimed to "build a clean and strong leadership and management, to overcome a huge risk that threatens the survival of our regime".
"We need a team of cadres and party members with good moral quality and ability," he said.
Overshadowed by scandal
The congress meets every five years to set the country's policies and strategy.
Over the next week, the 1,176 delegates will elect a new Central Committee of 160 members.
This committee in turn chooses the 15 to 17 members who will make up the powerful politburo.
Delegates will also, for the first time, be able to suggest candidates for a new general secretary.
Analysts expect that both President Tran Duc Luong, 68, and Prime Minister Phan Van Khai, 72, will announce their retirements during the congress.
There is also speculation that the 65-year-old Mr Manh will step down.
Other than the opening and closing ceremonies, proceedings will be closed to diplomats and the media, the AFP news agency reports.
Despite the red flags and banners adorning Hanoi's streets and buildings, the congress has been overshadowed by the corruption scandal of recent weeks.
Senior transport ministry officials are accused of embezzling millions of dollars of money meant for construction projects and using it to buy houses, cars, to bet on European football matches and for prostitutes.
In his resignation letter to the prime minister, Dao Dinh Binh said he was "very saddened and would like to take full responsibility for what happened at the ministry".