Ministry of Defence (MoD) officials are examining proposals for an army of 60,000 soldiers, former coalition defence minister Sir Nick Harvey has said.
Sir Nick said paper exercises were going on to examine further cuts to troop numbers due to the impending "financial crunch" faced by the MoD.
The Government's existing Army 2020 plans envisage a shrunken regular force of 82,000 with the number of reservists rising to 30,000.
Sir Nick told MPs: "There are already paper exercises going on in looking at what an army of just 60,000 would look like because of the financial crunch that the department is going to be facing."
The Liberal Democrat MP was speaking in the Commons during a debate on Trident renewal.
The upper age limit for some soldiers to join the Army Reserve has been increased by nine years to 52.
The Ministry of Defence (MoD) said the age limit for individuals with specific qualifications or experience has been raised from 45 to 50, while the maximum age for ex-regular soldiers joining was increased earlier this year from 43 to 52.
A spokeswoman said the MoD made "no apology" for revising the age requirements, adding, "All recruits have to meet strict fitness requirements, or could face discharge."
The upper age limit for ex-regular soldiers to join was increased in May to "better reflect demographics and health of the population" and widen the recruitment poo.
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The Ministry of Defence (MoD) has confirmed that an unmanned RAF 'Reaper' drone carried out attacks against militants in Iraq for the first time at the weekend.
The MoD said the drone was used during a series of coalition missions conducted near Bayji, north of Baghdad and "successfully attacked the terrorists using a Hellfire missile".
The drone also provided "intelligence, surveillance and reconnaissance assistance to coalition aircraft which enabled them to conduct further strikes" according to the MoD.
An RAF unmanned drone has been used for the first time in the ongoing fight against ISIS in Iraq.
First strike from an RAF unmanned drone (a Reaper) in Iraq against ISIS
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The Ministry of Defence said the "very presence" of coalition aircraft over Iraq has "a significant impact" on Islamic State’s efforts to attack locally.
"With no effective defence against air strikes, and knowing the precision with which coalition aircraft can hit them, the terrorists are forced to be much more cautious, keeping their forces dispersed and movement inhibited," a spokesperson said.
"They also know that should they concentrate to deliver an attack against Iraqi or Kurdish troops, aircraft are likely to arrive overhead very soon afterwards."
The Ministry of Defence has confirmed on Twitter:
The Ministry of Defence has posted on Twitter:
The MOD confirms RAF Tornados fly over Iraq from Cyprus following parliamentary approval. http://t.co/R663Hv0D6f
The Ministry of Defence has released footage showing the successful airdrops of humanitarian aid by the RAF in northern Iraq last night.