The upper age limit for some soldiers to join the Army Reserve has been 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.
An MoD spokeswoman said: " We make no apology for revising the age requirements for ex-regular soldiers to join the Reserves and share their wealth of knowledge and expertise. 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 pool, the MoD said.
The change comes as the Army's plan to cut regular troops and replace them with reservists came under fire yesterday, after it was revealed the size of the part-time force increased by just 20 in the last 12 months.
Figures showed the trained strength of the volunteer Army Reserve rose from 19,290 in October last year to 19,310 a year later.
Tory MP John Baron said the plans to replace 20,000 regular troops with 30,000 reservists were a "shambles" and shadow defence secretary Vernon Coaker warned the forces could be left with a "dangerous" gap.
The MoD said it expected to meet its target of having 19,900 trained members of the Army Reserve by April.
Sources acknowledged the targets were "challenging" but there had been an increase in new entrants who would take up to two years to fully train.
Basildon and Billericay MP Mr Baron, a former officer in the Royal Regiment of Fusiliers, said: "These latest figures confirm that plans to replace 20,000 regulars with 30,000 reservists are a shambles. Government attempts to get our defence on the cheap are on the ropes."
Mr Coaker said Government plans " are failing and there is a real concern that Britain's armed forces could be left with a dangerous capability gap as a result".
The trained strength of the tri-service Future Reserve 2020 volunteer reserve forces is 22,450, up by 400 since October last year, an increase of 1.8%.
In the six months from April 1 this year 2,130 people joined the Army Reserve, an increase of 62.2% compared with the 1,310 who joined in the same period last year.
Minister for Reserves Julian Brazier said: "Reservists make a tremendous and growing contribution to our armed forces, from assisting in the continuing mission in Afghanistan, the fight against Ebola, and closer to home, providing assistance to civil authorities, such as flooding relief earlier this year.
"We have always recognised that reinvigorating our Reserve Forces would not be achieved overnight. However, one year into our five-year plan we are making steady progress and seeing increased numbers joining the Reserves.
"By investing £1.8 billion in our Reserve Forces, fully integrating them with our regulars, and ensuring they receive the best training and equipment available, we are demonstrating our commitment to both our serving personnel and to enhancing the opportunities available to those joining in the future."