Warnings over flagship government projects
More than 30 of the coalition's flagship schemes, including Universal Credit and high-speed rail, are at serious risk of failure, a report says.
The government's Major Projects Authority (MPA) has given 32 schemes a red or amber/red rating, meaning they are deemed unachievable or in doubt.
Red projects include two £7bn aircraft carriers dogged by delays, and a new passport applications system.
The Cabinet Office welcomed the report and said it would lead to improvements.
The MPA was established in 2010 with the aim of turning around the civil service's "lamentable record" of delivering large schemes.
It is currently monitoring the status of projects worth £350bn and has assessed how likely they are to meet their time, cost and quality targets.
In documents released on Friday, the MPA warned that large portions of that public money could be at risk because of delays and inefficiencies.
Of 191 programmes assessed, 32 were given the green all-clear rating - meaning successful completion is "highly likely" - with 49 classed as amber/green, meaning success is "probable".
Some 58 were amber - which means success is "feasible" but significant issues exist - and 21 were exempt from ranking.
Eight red projects - meaning those deemed "unachievable" as a result of budget, schedule or delivery problems - include the refranchising of the West Coast Main Line scheme.
In October, the government scrapped its decision to award the £5bn franchise to FirstGroup, meaning Virgin Trains will continue running the service until November 2014, when a new long-term franchise is due to begin.
Also among the red projects were: Watchkeeper, a new unmanned aerial vehicle for the Army; a new computer system for the Ministry of Justice; and a new system for the Home Office to manage passport applications.
Some 23 schemes were given an amber/red rating, meaning their successful delivery is "in doubt" and urgent action needs to be taken.
They include some of Work and Pensions Secretary Ian Duncan Smith's welfare reforms, such as the introduction of the Personal Independence Payment - the replacement for Disability Living Allowance - and the controversial benefit cap, limiting the maximum amount any household can receive.
In a number of cases highlighted by the MPA - including Universal Credit - the government said the data used to rate the projects was now six to 12 months old and things had improved considerably since then.
The HS2 high-speed railway line, linking London with Birmingham and Manchester at a current estimate of £33bn, was also designated amber/red.
Last week, the National Audit Office warned the economic benefits of the vast project were unclear.
Cabinet Office Minister Francis Maude said the MPA had already helped to save more than £1.7bn.
He said that, when he came into government, there was "a relaxed approach to managing projects worth hundreds of billions of pounds" with problems "swept under the carpet where they festered at the taxpayers' expense".
"Since the general election we have got things back on track and are equipping the civil servants with the skills they need," he said.
He added: "There's much more to do but thanks to the work of excellent officials we now expect to double the success rate of major projects, compared with the figures from 2010."
But shadow Cabinet Office minister Gareth Thomas told the BBC: "The most striking thing is just how many huge government projects are off track and are at risk of not being delivered, and the sheer scale of public money that's at risk."
Mr Thomas also accused the government of trying to hide the MPA's findings.
"It was slipped out at five o'clock on a Friday, when Parliament wasn't sitting, so preventing Members of Parliament from getting to grips with the detail in this report," he said.
And Matthew Sinclair, chief executive of the Taxpayers' Alliance, also said the timing of the report's release would "only add to suspicions that the government was trying to bury bad news".
"Alarm bells will now be ringing yet again for taxpayers over central government's ability to deliver value for money on some of its multi-billion pound projects," he added.
Data for the latest report was gathered between June and September 2012, and at the time of assessment, some projects were still at the planning stage, others were ongoing, and some were already complete.