The Home Office has questioned Liberal Democrat advice to people to renew their passports now to avoid inclusion on the ID card database for 10 years.
The Home Office insists the ID card database will be 'built from scratch'
Anyone requesting a new passports from 2008 will have their details stored on the National Identity Database.
The Lib Dems are urging people to act in "the coming weeks" to avoid this.
But the Home Office said it was "hard to see what would be achieved" by making applications in advance, "other than incurring unnecessary expense".
The Lib Dems say by applying for a passport now you can avoid appearing on the ID database until 2016.
By then, the theory goes, the Lib Dems or Conservatives - both whom have pledged to scrap the ID scheme - could be in government.
The Lib Dems are backing the "Renew for Freedom" campaign of pressure group NO2ID.
People can apply now for a new passport that will last until May 2016, regardless of the expiry date of their present document.
'Expensive, intrusive, ineffective'
Five Liberal Democrat MPs staged a photocall at the Passport Office in Victoria, London, on Wednesday to highlight their argument.
Home affairs spokesmen Nick Clegg, Lynne Featherstone and Mark Hunter were joined by party president Simon Hughes and rural affairs spokesman Roger Williams.
Mr Clegg, whose own passport is not due for renewal until October 2012, said: "ID cards will be expensive, intrusive and ineffective.
People can buy themselves '10 years freedom' from the database
"I urge everyone who is concerned about their introduction to join the NO2ID 'Renew for Freedom' campaign and renew their passport over the coming weeks.
"The Liberal Democrats were the only party to vote against the introduction of identity cards and we're making our opposition clear today by buying ourselves 10 years of freedom from this unnecessary scheme."
The Home Office spokesman said nobody would be registered on the database until its launch because "it will be a clean database built from scratch".
"We will not be importing existing information from other databases such as the passport database," he said.
The Identity Cards Act was introduced earlier this year, following a rocky passage through the House of Lords.
Once the National Identity Database is set up, everyone who applies for a passport will have to attend an interview, provide fingerprints and have their irises scanned.
They will save some fees by paying the current £51 charge for renewals instead of the minimum £93 the Home Office says passports will cost when the database is in operation.
Biometric details will be taken and stored from people renewing or getting passports from 2008.
They will be able to opt out of having an ID card for two years but will still appear on the ID database and will have to pay the same price as someone receiving a card.
From 2010 anyone renewing or getting a passport will have to get an ID card.