Tax evasion, benefit fraud, false accounting and theft – just some of the things Lambeth Council employees and contractors were investigated for in the past two years.

Opposition councillors said fraud was “endemic” within the council, while the council said it had an excellent track record on tackling the issue.

According to a report submitted to Lambeth Council’s corporate committee last week, up to 30 officers have been investigated for various wrongdoing in 2010 and 2011 – though a council spokesman said some of the cases involved contractors.

Of those, five were found guilty of fraud and 19 were disciplined for professional misconduct. Two officers were sacked and four resigned after being found guilty of corporate fraud.

Another employee was charged with fraud following an appeal against a parking charge notice and penalty fee.

Separately, a further two officers received written warnings for similar cases of wrongdoing, while 13 people suspected of fraud are yet to hear whether they will keep their jobs.

More recently, two officers were arrested for their alleged involvement in fraudulent activities.

The officers, who held positions within the council’s housing and regeneration department and within children and young people’s services, have subsequently resigned or been dismissed from their jobs.

Police enquiries into both cases are ongoing.

Councillor Peter Truesdale, Liberal Democrat spokesman for finance, said internal fraud at the council was “endemic”.

He said: “It is worrying to see Lambeth still fighting against widespread fraud practices. It is like having a bug that destroys your immune system, so no matter how you fight it off you just cannot do it.”

But the council’s cabinet member for finance, councillor Paul McGlone, said the report reflected the council’s “rigorous approach” to rooting out fraud and said their investigations were saving taxpayers “thousands of pounds every year”.

He said: “Lambeth has an excellent track record in tacking fraud. We have well publicised whistle-blowing procedures that ensure any wrongdoing committed by staff is exposed and dealt with.”

It is not the first time the council has hit the headlines for cases of internal fraud.

In June last year, former Lambeth Living chairwoman Asuman Ozkan avoided jail despite pleading guilty to 13 charges of fraud and deception.

The former chairwoman dishonestly claimed nearly £90,000 in income support, housing and council tax benefits, as well as a £38,000 discount to buy a £140,000 council flat in Clapham.

Meanwhile in a separate case, councillors revealed former housing contractor Alex Watson-Jones, who was allegedly responsible for a £3m fraud against the council in 2005, also worked on the failed Roupell Park boiler project.

The combined heat and power (CHP) boiler, which aimed to provide efficient heating to 569 homes, was never completed, and an estimated £5m.

The council is seeking to bring a prosecution against Mr Watson-Jones and has written to the Justice Secretary to press the case.