The Conservatives have accused the government of burying the cost of ID cards in a hike in the price of passports.

Yesterday the government announced an increase in the price of a 10-year adult passport from £72 to £77.50 in the first passport fee rise for passport services in the UK since 2007. There will also be a rise of £3 to the cost of a child’s passport to £49.

The Home Office said the price hike was needed because demand for passports had fallen, but Conservative shadow home secretary Chris Grayling said the move appeared to bury part of the cost of the ID scheme in the price of a passport.

"The government admits that it has no idea how many people will have to volunteer for ID cards before they cover their costs, so it looks like the cost is being lumped onto our passports," he said.

Both passports and identity cards are funded from the same agency, the Identity and Passport Service, which is part of the Home Office.

The government has always maintained that many of the technology systems used for identity cards would also be used for biometric passports – including the biometrics national identity register.

In April, IBM was awarded a £265m deal to build this biometrics database to support ID cards and passports, while CSC has been given a £385m deal to upgrade the application and enrolment system, which is intended to be used for both passports and ID cards.

A home office spokesman rubbished the claims.

"Passport fees only recover the operational costs incurred in processing passport applications and are not used to recover any costs of other IPS operations, such as the production of GRO certificates or the delivery of National Identity Service," he said.

Earlier this week, home secretary Alan Johnson insisted the government was still committed to the ID card scheme despite plans to issue the second batch of cards to airside workers at Manchester and London City airports being abandoned.