An extraordinary, some may say scandalous, outcome of the splurge of figures released by the government this week is the amount of money being spent on weapons systems that the armed forces cannot use, do not need, and even do not want.

In the days leading up to their defence review and overall government cuts package, David Cameron, George Osborne and the defence secretary, Liam Fox, all tore into what they described as the shambolic and chaotic state of the defence budget. Former successive defence ministers and chiefs of staff, egged on by arms manufacturers, bottled out of tough decisions, indulging in a spending spree that left a £38bn black hole in the weapons procurement budget.

Yet they are punished even less than the bankers for their profligate irresponsibility. The navy gets two large aircraft carriers – the biggest ships it has ever had – at a cost of more than £5bn. The first one, the Queen Elizabeth, is due to enter service in 2016 yet, because Britain's Harrier fleet is being scrapped and the expensive US Joint Strike Fighters (JSFs) due to replace them won't be ready in time, by 2020 the ship will be mothballed – or sold – without ever having planes flying off her.

By 2020, the second carrier, the Prince of Wales, should be ready but adapted to take cheaper, catapult-launched JSFs, or French Rafale planes. So, for the next 10 years, Britain will have no carrier-based strike force. The obvious question, which has not been satisfactorily answered by the government, is why such a threat needing such a force will suddenly face the UK in 10 years' time. Cameron, with seemingly genuine outrage, told the House of Commons that it would be cheaper to build the second carrier than cancel it, thanks to the nature of the contract signed by the Ministry of Defence with the manufacturers' consortium led by BAE. At least it was one decision the unions did applaud in this week of cuts.

The carrier fiasco is not the only bizarre feature of the government's strategic defence and security review. A new Nimrod maritime reconnaissance aircraft will be scrapped even though £3.6bn – about the amount of money the entire defence budget will be cut by over the next four years – has already been spent on it. At least this was one decision not to throw good money after bad.

Meanwhile, the RAF, the National Audit Office told us, will get 16 more Eurofighter/Typhoon jets than it has asked for at a cost of £2.7bn because it would be cheaper to build them than cancel the order, again because of the contract signed with the makers.

And then there was Trident, a nuclear missile system costing at least an initial £20bn, which we were told had to be ordered now. In a politically convenient move – the Lib Dems are split on the issue and at least demanded that a decision be put off – no decision on how exactly to replace the existing fleet of four Trident submarines will be taken until 2016, after the next election.

And the Treasury has forecast that the cost of military operations in Afghanistan, which have already cost £12bn, will cost an additional £15bn over the next four years.

Excluding Trident, the projects and operations mentioned here will cost more than £26bn, something that should not be forgotten. The sum amounts to nearly half the cuts announced by the chancellor on Wednesday.