MPs have voiced doubts about the credibility of the coalition's £310 billion plan for boosting Britain's infrastructure.
The Public Accounts Committee said the Treasury had not properly prioritised 200 key projects, and urged ministers to be "realistic" about how much private and public investment can be raised as the economy stalls.
It also warned that consumers will shoulder the main burden of the costs through higher rail fares and utility bills.
The criticism came in a report into the National Infrastructure Plan, which was launched in 2010 and last updated in December. It listed projects costing a total of £310 billion - with around £200 billion of that expected to be wholly funded by the private sector.
The committee stressed that investment in power generation facilities, roads, railways, airports, ports and communication systems is "crucial for stimulating economic growth". But it added: "We are not convinced that a plan requiring £310 billion of investment in infrastructure is credible given the current economic climate, the cutbacks in public finances and the difficulty in raising private finance for projects on acceptable terms."
The Treasury says it has prioritised 40 programmes, but many of those cover broad areas and there are actually 200 individual projects "whose relative priority is not clear", according to the committee.
PAC chairwoman Margaret Hodge said: "The Treasury's Infrastructure Plan is simply a long list of projects requiring huge amounts of money, not a real plan with a strategic vision and clear priorities. Most of the £310 billion of investment needed will come from the private sector, with households shouldering the cost through higher energy bills and fares."
A Treasury spokesman said: "We do not agree with the committee's depiction of the Government's infrastructure delivery plans. Planning and delivering vital long-term infrastructure is a central economic priority. That's why we launched the first ever National Infrastructure Plan, setting out a strategic approach that monitors the performance of our key infrastructure sectors and identifies the projects needed to build an economy fit for the future.
"Government regularly monitors progress and at the Budget published details of delivery of the top 40 infrastructure projects. As well as switching billions of pounds from current to capital spending, we are also using the Government's balance sheet to provide vital funding. Last week, Drax Power became the first recipient of a UK Guarantee, with the Treasury underwriting £75 million of investment in biomass energy."
Shadow financial secretary to the Treasury Chris Leslie said: "Our economy is flatlining with David Cameron and George Osborne giving us the slowest recovery for 100 years. We urgently need a plan for jobs and growth, including bringing forward infrastructure investment and building thousands of affordable homes. This is vital if we're to kickstart our economy and strengthen it for the long-term."