* None of country's submarines ready for combat for 5 months in 2018
* Helicopters, combat jets still at low levels
* Lawmakers chafe at decision to classify report (Adds details and quotes from Zorn, opposition reaction)
By Andrea Shalal
BERLIN, March 11 (Reuters) - Germany's military remains dissatisfied with the combat readiness of its submarines and certain older aircraft, but a spate of reforms are starting to take hold, the military's top uniformed officer told lawmakers on Monday.
However, in a letter accompanying the military's annual readiness report, Inspector General Eberhard Zorn said the actual report would be kept classified for the first time for security reasons, a move criticised by opposition lawmakers.
"Apparently the readiness of the Bundeswehr is so bad that the public should not be allowed to know about it," said Tobias Lindner, a Greens member who serves on the budget and defence committees.
He asked parliament to postpone consideration of the mandatory report - which can be seen only in a secure facility - until next week, instead of Wednesday, to give lawmakers more time to study its conclusions.
Zorn said the average readiness of the country's nearly 10,000 weapons systems stood at about 70 percent in 2018, which meant Germany was able to fulfill its military obligations despite increasing responsibilities.
No overall comparison figure was available for 2017, but last year's report revealed readiness rates of under 50 percent for specific weapons such as the ageing CH-53 heavy-lift helicopters and the Tornado fighter jets.
Zorn said this year's report was more comprehensive and included details on five main weapons systems used by the cyber command, and eight arms critical for NATO's high readiness task force, which Germany heads this year.
"The overall view allows such concrete conclusions about the current readiness of the Bundeswehr that knowledge by unauthorised individuals would harm the security interests of the Federal Republic of Germany," he wrote.
Zorn said changes meant to boost availability of spare parts and cut maintenance times were producing results, at least in some areas.
None of Germany's six U212A submarines were ready for operations for five months in the first half of 2018, although the number rose to three by the end of the year, he said.
The readiness levels of the CH-53 helicopter and Tornado fighter jets remained at the low levels seen in 2017, when an average 16 of 72 CH-53 helicopters were combat-ready, and 26 of 93 Tornado fighter jets.
This underscored the importance of moving forward with replacement programmes for both weapons, Zorn said.
Some improvement was seen in the readiness of the GTK Boxer ground vehicle, and the A400 military transport, he said. (Reporting by Andrea Shalal Editing by Tassilo Hummel and Frances Kerry)