The Liberal Democrats have called for a “full debate” on the way the government uses its huge databases in the wake of a series of new data sharing proposals by ministers.

Nick Clegg UK Member of Parliament, the Liberal Democrat home affairs spokesperson, made the call after uncovering details of disagreements within the government about moves to pass automated number plate recognition (ANPR) data from congestion charging and future road pricing cameras to police.

Details of the plans – and disagreements – were in a document inadvertently released by the Home Office as it made a formal announcement that Transport for London would share the ANPR data gathered for the capital's congestion charging scheme with police.

The London move required home secretary Jacqui Smith to sign certificates exempting the transport body and the Metropolitan Police from provisions of the 1998 Data Protection Act.

Prime minister Gordon Brown has also slipped new powers for government departments to share data held on major databases into proposed new legislation on terrorism, education and skills and the sale of student loans, ComputerworldUK revealed last week.

Clegg said the release of the Home Office document revealed “the disingenuous attitude of ministers towards public fears about a creeping surveillance state”.

“Bit by bit, vast computer databases are being made interoperable and yet the government seems to be running scared of a full and public debate on the safeguards needed to make such information-sharing acceptable,” he said.

Clegg added: “The government appears to be using the London cameras as a Trojan Horse to secure unprecedented access to information on car drivers' movements without full public scrutiny or debate.

“It is high time for a full debate on the use of information databases by this government.”