Billions of pounds worth of government projects are at risk of failing.

The government is confident of delivering just 20% of its projects, new report claims.

And that's before Brexit-related projects are added to the pile.

Chopping and changing at ministerial level is harming Brexit preparations.

LONDON — Theresa May's government is confident of successfully delivering just one-in-five of its major projects, according to a worrying new report out today.

Analysis of official government risk assessments by The Institute for Government has found that 80% of projects across various government departments are classed as being either in doubt, hindered by problems, or virtually unachievable.

Worryingly for Prime Minister Theresa May and her Cabinet, the bulk of projects in question does not include the majority of Brexit-related projects that will need to be delivered urgently, in areas like immigration and customs.

There could be up to 14 Brexit-related projects that "would be critical for immediate implementation" as soon as Britain leaves the European Union, according to National Audit Office research cited in the IfG report.

The total cost of projects is £455 billion, according to the IgG. However, the government doubts whether four-fifths of them will be delivered, which raises the question of how much public money could be wasted on failed projects.

A third of projects with costs over £1 billion are either in doubt or seen as unachievable.

The IFG based its research on data published in the Infrastructure and Projects Authority's annual reports.

Here is a chart produced by the IgG:

Responding to the report, a spokesperson for the IPA told Business Insider that assessments of projects are taken at a specific point in time, and that their status is subject to change depending on what action is taken.

A spokesperson said: "If a project is rated Red or Amber/Red, it doesn't mean it will continue to be unachievable, rather at that point, assuming no mitigation actions are taken.

"The IPA provides assurance and support to improve delivery confidence and likelihood of success."

Government instability has harmed Brexit preparation

The IfG report also concluded that high turnover at ministerial level has disrupted Brexit planning.

It found that 85 out of 122 ministers have been moved to a new post since the June general election.

This includes in the Justice Department which has had six secretaries of state since 2010, and the Department for Work and Pensions, which has had five in just three years.

"New ministers will need to get up to speed quickly to face the challenges in public services, major projects and Brexit," report author Gavin Freeguard said.

The report adds that the delay to the EU (Withdrawal) Bill in passing through Parliament is leaving little time for the government to pass up to 1,000 pieces of secondary legislation needed for Britain's exit from the EU.

This process, the IfG claims, could take over 100 days of Parliament.