Retired Royal Navy submarines lined up in Devonport.
The Royal Navy's retired fleet of submarines is costing the taxpayer £30 million per year in storage and maintenance costs, a new report has found.
The report by the Commons Public Accounts Committee said the Ministry of Defence's failure to dismantle the submarines is "unacceptable and unnecessary".
The UK retired its 20 legacy submarines in 1980, with nine of those still containing nuclear fuel.
Meg Hillier MP, chair of the committee, said since then the MOD has spent £500 million on the storage and maintenance of the retired submarines.
The report by MPs also warned the MOD is likely to find itself without any further storage space by the mid-2020s.
Ms Hillier told Forces News there "could be an impact" on the UK's defence capability as a result.
She said: "The less space there is, the harder it is to maintain the existing fleet."
The report also said the Department is "rapidly approaching crisis point and simply cannot afford any further delays".
It found the MOD's target to dismantle its first submarine, HMS Swiftsure, by 2023 will not be met and is likely to be three years late.
Ms Hillier said the issue is "getting urgent" but the report did say it was "encouraging" to see progress being made in the project.
Ms Hillier said: “Whilst some progress has been made recently with submarine disposals, the MOD cannot afford to fall any further behind.
“The Public Accounts Committee has set out a series of milestones for the MOD to ensure that it keeps on track to establish submarine disposal as a routine part of its business."
The report also said the MOD's budget 'black hole' of at least £7 billion is likely to make the task more challenging.
The MOD currently has twice as many retired submarines as it does in active service.
An MOD spokesperson said: "The disposal of nuclear submarines is complex, but we are committed to ensuring they are disposed of safely, securely and cost-effectively and have already made progress."