The UK Government's commitment to a national identity scheme appeared to be hit by doubt last night after a minister admitted that plans for a computerised register would need to be "reassessed" in wake of the data security scandal.

Michael Wills, the Data Protection Minister, said the disappearance of the two computer discs containing the personal details of 25 million people in transit from HM Revenue and Customs offices in Tyne and Wear to the National Audit Office in London had been "deplorable".

Giving evidence to Westminster's Joint Commons and Lords Human Rights Committee, he acknowledged that it would have implications for the planned national identity card scheme backed by a national identity register.

He said: "We are going to obviously have to look at the national identity register in the light of all this. We are going to have to learn the lessons. Everything will have to be scrutinised and then we will assess it again."

However, Mr Wills drew back from a suggestion by the Conservative peer Lord Onslow that the UK Government would have to abandon the scheme altogether if it became clear that the risks of a data security breach were too great. "With all these things there are very complicated trade-offs that have to be made," he said.

Following last week's revelations about Britain's biggest loss of confidential data, Opposition MPs demanded Prime Minister Gordon Brown scrap the planned national ID card scheme while Labour colleagues called for a pause and reflection on the multi-billion pound scheme.

Earlier in the Commons, Jacqui Smith, the Home Secretary, was forced to defend the security of data under the proposed ID cards scheme after the loss of the confidential child benefits records.

She told MPs that the use of biometric information on the ID card would be an "important protection" and the data would be held separately from personal details.

However, David Davis, her Conservative shadow, claimed that personal details could be shared with the 27 other EU nations under a pilot Europe-wide project.

"The Home Office is currently prototyping a Europe-wide project called Project Stork. How are we going to prevent a repetition of the disaster of the last few weeks when sensitive personal data is held not by one government but by 27?" asked Mr Davis.

Ms Smith said she would be willing to follow up Mr Davis's allegation if he would provide further details.

Today, Alistair Darling will seek to place the woes befalling the UK Government in the overall context of a strong, thriving economy, achieved by 10 years of Labour rule.

Speaking at the CBI conference, the Chancellor is expected to say: "This government's determination to take the tough decisions means that even in today's uncertain times - with turbulence in international financial markets and record oil prices - we can be confident of the resilience of the UK economy."

On Northern Rock, he is due to say: "I believe it was right to intervene. That it was right to put in place guarantee arrangements for savers and above all it is right to see it through. It was never going to be an easy decision."