Taxi licences are being issued behind closed doors to drivers convicted of offences including child sex crimes and reckless driving, the Local Democracy Reporting Service has revealed.
The findings follow a government report that claims current taxi and private hire laws are "not fit for the modern world".
According to the report, rules need tightening on everything from CCTV use in taxis to criminal record checks.
Some existing laws date back to 1847.
In most areas licences for taxis and private hire vehicles - or minicabs - are issued by unitary, borough or district councils. In London the system is managed by Transport for London.
In recent weeks, Local Democracy Reporters have reported that:
The Bolton News also reported that licensing chiefs let a taxi driver off with a warning - also in private - after he was convicted of driving without due care and attention and failing to stop after an accident.
Bury Council, however, refused to give a private hire licence to a driver accused of sexual assault, even though he was later found not guilty of the allegations.
As the licensing authority, many councils hold the hearings in private under local government rules about protecting personal information.
They have to decide if someone is "fit and proper" before granting a taxi or private hire licence. Although guidance has been published by the government and Local Government Association there are no legal rules on how to determine a "fit and proper person".
Steve McNamara, general secretary of the Licensed Taxi Drivers' Association (LTDA), said the industry "urgently needs" new laws with strict standards, a national database of drivers and operators, and an end to "cross-border" hiring that sees drivers working outside the area where they are licensed.
He added: "These drivers clearly fail to meet the 'fit and proper person' test and should never have been in a position to drive members of the public. The current flawed system is being exploited by unscrupulous private hire drivers and operators who disregard regulations to work wherever and however they want.
"The outdated system must be overhauled to give passengers confidence that they will be safe whenever they step into a taxi or minicab."