The Tories’ were today urged to “get a grip” on key defence equipment programmes after costs rocketed by £9billion in just one year.
Research revealed experts had doubts over whether a raft of major military projects could be delivered on time and on budget.
The analysis of the Government Major Projects Portfolio comes as Rishi Sunak prepares to fly to Lithuania on Tuesday for a crunch NATO summit which will be dominated by the alliance’s support for Ukraine.
The Prime Minister is expected to trumpet latest figures showing the UK was one of just 11 NATO countries in the 31-member organisation to meet the alliance’s target of nations spending at least 2% of GDP on defence.
But Britain barely scraped over the threshold, with just 2.07% allocated to the armed forces, according to NATO statistics released last week.
A study by the Lib Dems of the most recent Infrastructure and Projects Authority annual report found that, of major defence schemes in the pipeline, lifetime costs have soared from £63bn in 2020-21 to £72bn in 2021-22.
The watchdog uses a traffic light system to rank the likelihood of a major project achieving its aims, on time and within budget.
Just three out of 52 Ministry of Defence projects were awarded the top green grade, while 33 were rated amber and nine got the worst red status, according to the 80-page report.
Schemes rated red include the delivery of F-35B, Lightning II fighter jets, with ministers still unclear how many warplanes they will buy.
The Core Production Capability programme, which aims to deliver nuclear reactor cores to Royal Navy submarines, was also graded red.
Another deal assessed as being red was the £5.5bn Ajax armoured vehicle contract as part of the Armoured Cavalry 2025 programme.
The Ajax contract promised to deliver 589 armoured vehicles, with the first due to enter service in 2019.
The Ministry of Defence insisted in February the scheme was back on track after initial tests left soldiers with hearing damage caused by excessive vibration.
Vital upgrades to HM Naval Base Clyde, which is home to the Royal Navy’s nuclear-armed Vanguard submarine fleet, were also deemed red, as was a project to fit a Crowsnest airborne surveillance and control system to Merlin helicopters.
Lib Dem defence spokesman Richard Foord, who served as a Major in the Army, said: “The Prime Minister needs to urgently get a grip on defence procurement.
“The Government’s own report makes for sobering reading; these delays are leading to ballooning costs.
“Getting procurement right is necessary at the best of times but is vital at a time when there is a war on the European Continent.
“We want to properly support Ukraine, but we also need to ensure that problems with Britain's defence procurement are being properly tackled.”
A Ministry of Defence spokesman said: “Any claim there are frequent delays or overspend on current Defence projects is inaccurate.
"The IPA report shows the majority it assessed can be successfully delivered on time and within budget."
* Follow Mirror Politics on Snapchat, Tiktok, Twitter and Facebook
