Newspaper report reveals battalions to be lost two days before official statement by defence secretary

The acrimony and chaos surrounding plans to cut 20,000 troops from the army have been laid bare after details of the battalions to be scrapped were leaked before a ministerial statement on Thursday.

The proposals, whose publication has been delayed by Downing Street because of their sensitivity, show historic units to be axed include the third battalion of the Yorkshire regiment and the Argyll and Sutherland Highlanders, the fifth battalion of the Royal Regiment of Scotland. One battalion will be lost from the Royal Welsh, the Mercians and the Royal Fusiliers.

The details reveal the units recruited in Wales will be hit as hard as those in Scotland – the government had feared giving the Scottish Nationalist party a political advantage by targeting regiments north of the border, but dared not spare all of them, particularly as some have struggled to attract recruits.

Official letters to army commanders were sent out on Tuesday, ready for the announcement in parliament by the defence secretary, Philip Hammond. The hope had been that soldiers would hear about the cuts from senior officers, but this has been dashed by the leak in Tuesday's Sun.

Some army chiefs are furious that the restructuring process is being used as a political football, with, they say, little regard for the troops whose livelihoods have been put at risk.

Insiders insist the military had wanted the plans published four months ago, but say Downing Street prevaricated because of the likely public backlash, and because it could not decide whether to push through the extra redundancies quickly, or spread them out between now and 2018. The army wants to press ahead with redundancies in order to address the pain as quickly as possible.

One Whitehall source said: "The decisions have been made and the army has been saying it just wants to get on with it. But politics has got in the way."

The army is losing a fifth of its overall strength because of budget cuts and restructuring set out in the much criticised 2010 Strategic Defence and Security Review.

A subsequent MoD re-evaluation – last year's so-called "three-month exercise" – more than doubled the number of troops to be lost to 20,000.

Decisions about how this should be done were left to Major General Nick Carter, who was asked to conduct a comprehensive rethink of how the army is run.

The Carter reforms, to be outlined in the statement on Thursday, will split the army into three distinct bodies; reaction forces, adaptable forces, and force troops.

The reaction forces will be the army's spearhead and will be trained, equipped and prepared for speedy intervention operations anywhere in the world. They will include the Royal Marine Commandos and the Parachute Regiment.

The adaptable forces would take over from the reaction forces, but would take 18 months to prepare for combat. They will be made up of existing full-time regiments and reserves.

Underpinning both will be the "force troops", or "theatre troops", which will be made up of all the units required to support the front line – such as the artillery, engineers, signals, intelligence and medical corps.

The restructuring is a radical move, and Carter also had to recommend which units were necessary, and which could be surplus to requirements with the cuts demanded by the Treasury.

There has been speculation in Westminster for weeks about which battalions would be axed, and the manner of their disclosure will infuriate commanders who have been preparing to address soldiers on Thursday morning.

The battalions to be saved include the Royal Scots Dragoon Guards, the Queen's Dragoon Guards and the Royal Dragoon Guards. The Parachute Regiment's three battalions will be spared.

Under the proposals, the Queen's Royal Lancers will be merged with the 9th/12th Lancers, and the 1st Royal Tank Regiment with the 2nd Royal Tank Regiment.

Responding to recent leaks about the cuts, the shadow defence secretary, Jim Murphy, said: "The government is presiding over an erosion of trust and a decline in military morale. The impact on capability and the criteria used for Army changes must be clearly explained. Tough decisions are necessary, but ministers' continued speculation and delay has only heightened uncertainty and a sense of disarray. The government must ensure that anyone made redundant is provided with post-service opportunities, including for service families." The MoD said it did not comment on leaks.