Wilmer Azuaje was a young firebrand when he joined Hugo Chávez's revolution a decade ago to topple Venezuela's corrupt ruling class. He was elected to the national assembly and worked with the president's family to turn their home state of Barinas, a rural backwater of cattle ranches, into a laboratory of change.

Azuaje was inspired by Chávez's promise to sweep away a history of graft and patronage which had stunted an oil-driven economy. "I believed in the process of reform," said Azuaje.

Not anymore. The baby-faced protege, once a rising star in the ruling party, has now become the Chávez family's most outspoken foe. "They turned out to be the most corrupt ever. They betrayed us."

Azuaje has blown the whistle on what he claims is a kleptocratic dynasty in Barinas where farms, businesses, banks and government contracts have been pocketed by the president's parents and five brothers.

The allegations come amid wider complaints that the revolutionary socialist movement known as "chavismo" has been hijacked by money-driven opportunists inside, or close to, the government.

Nationalisations, the creation of new state enterprises and a maze of price and currency controls have spawned well-connected millionaires nicknamed Boligarchs, after the independence hero revered by Chávez, Simón Bolívar .

Murky state finances meanwhile have put Venezuela 162nd, alongside Angola and Congo, out of 180 countries in Transparency International's corruption perceptions index.

Chávez appears to have recognised the wheel has turned: that the cry against corruption which helped bring him to power in 1998 will be used against his candidates in September's legislative elections. "This party has to tighten the moral belt," he said in December last year.

The charismatic leader remains popular with many of the poor for spending oil revenues on social programmes but with the economy shrinking and widespread electricity and water shortages the perception of sleaze could tip the balance against his PSUV party. Some 64% think corruption has worsened and regard things to be generally going badly, according to a recent poll.

For Chávez it is especially galling that Barinas, the family fiefdom and revolution showcase, is now cited for corruption, nepotism and misrule. Critics have a list of grievances and accusations which make the state's administration sound like a soap opera.

Chávez's father ruled as governor for a decade until handing over to the president's brother, Adán, in an election marred by fraud allegations. Other brothers are also thriving: Aníbal is mayor of nearby Sabaneta; Adelis is a top banker at Banco Sofitasa, which enjoys government contracts; Argenis wields enormous clout as a political fixer; Narciso is reportedly planning his own election run.

Members of what is dubbed the "royal family" travel in convoys of 4x4s. The president's once-matronly mother, Elena, has had a makeover with plastic surgery, designer clothes, bling jewellery and a poodle named Coqui.

It is alleged the family bought thousands of hectares of farmland through proxies, including a former labourer, Nestor Izarra, who is named as the owner of one estate, La Malagueña. The family has denied any wrongdoing.

The cost of a football stadium built under Adelis Chávez's supervision ballooned to $93m (£60m) and remains unfinished three years after hosting its first game. A Venezuelan-Cuban sugarcane project has been mired in a $1.5m embezzlement scam. The state government uses emergency decrees for public works which bypass open tender requirement and allegedly reward cronies.

Crime, notably kidnapping, has exploded, with even the middle class and poor falling prey to gangs which brazenly abduct victims from roads, shopping malls and universities. You are four times likelier to be kidnapped in Barinas than Colombia or Mexico.

"The courts have collapsed, there are backlogs for everything," said Pedro Pablo González, a lawyer and political activist. "There are not enough investigators, prosecutors or police, it's a mess." He recently led a 19-day 500km protest walk to the capital, Caracas.

Many local "chavistas" have defected to the opposition. "Really, it became too much," said Lorenzo Saturno, a legislator who quit the ruling party. "Corruption is out of control and the Chávez family has total impunity."

Loyalists say that is a smear which overlooks new roads, houses, schools and employment projects dotting Barinas's plains and dusty towns. Why else would voters keep the Chávez family in power, said Miguel Angel León, president of the regional legislative council. "This is a happy, dynamic state. The football stadium, for instance, is about to be finished. But a few protesters are able to manipulate the media to make Barinas look bad," he told the Guardian.

Other loyalists say the president proved his anti-corruption credentials during a banking scandal last December when he purged a senior minister, Jesse Chacón, and businessmen with ties to the government. "We are demonstrating that there are no untouchables here," Chávez said at the time.

Sceptics said the shakeup owed more to a feud between rival ruling factions than a crackdown on sleaze. And that the fate of whistleblowers showed there were indeed untouchables.

Luis Tascón, an ultra-chavista legislator, was expelled from the ruling party and called a traitor after accusing senior officials of corruption.

Azuaje (left), the Barinas firebrand, has had a torrid time since delivering to the national assembly a package of pictures, deeds and documents which he said proved the Chávez family amassed an illicit $20m fortune. The government-controlled assembly dismissed the claims after a brief inquiry.

The 33-year-old legislator said he then reaped a whirlwind: shots fired at his home; a brother killed; his mother and wife fired from state jobs. The latest alleged reprisal: a criminal charge that he abused and struck a policewoman.

The national assembly recently lifted Azuaje's immunity as a lawmaker, an unusual step, after which he was handcuffed and briefly detained. The supreme court also barred him from publicly discussing the charges. It is unclear if he will be able to run in September's election. "This is about revenge, clear as day. Chávez has not forgiven me for accusing his family," he said.

Amnesty International said the government was using the judiciary to persecute Azuaje and other opponents. "Charges brought for political reasons against critics are being used to silence dissent and prevent others from speaking out," the watchdog claimed last week.

Chávez supporters claimed that was unfair. People suspected of crime were being brought to book, as simple as that, wrote Eva Golinger, editor of the state-backed newspaper Correo del Orinoco International.

"Ideology is not an exemption from criminality. After a lengthy period of impunity in Venezuela, the judicial system is finally beginning to risk imposing the law, at whatever cost."