MPs have criticised a catalogue of costly government computer problems which have had a "direct impact" on the public.

A report by the Commons Public Accounts Committee identified more than 25 cases over the last decade which resulted in delay, confusion and inconvenience or represented poor value for money.

The blunders included last year's fiasco at the Passport Agency when problems with the introduction of a new computer system led to a backlog of more than 500,000 unprocessed applications.

Ministers were forced to apologise for the chaos as emergency measures were introduced to enable the public to get passports at post offices.

A damning report by the National Audit Office reported that the crisis would cost the taxpayer about £12.6m.

That bill included £6m spent on staff overtime and at least £161,000 to compensate hundreds of people who missed their holidays because they did not receive their passport on time.

The agency also spent £16,000 on umbrellas for people queuing in the rain outside passport offices to get their documents over the counter.

However, even greater misery has been caused by the introduction of a new computer system for recording National Insurance payments.

Failures in the new IT venture led to 17 million contribution payments not being registered on claimants' records.

As a result 172,000 pensioners were underpaid their pensions by between a penny and £100 per week.

The final bill for compensation is expected to top £40m.

Teething troubles with another new network have also caused red faces in the Home Office's Immigration and Nationality Directorate.

The faults have contributed to the build up of a backlog of 76,000 unprocessed asylum seeker cases and 100,000 nationality cases.

However, some of the government's most costly computer blunders never even made it into service.

The Ministry of Defence's planned "Trawlerman" computer system for handling classified documents was eventually deemed unviable and had to be abandoned completely at a cost of £41m.