"The publication of the data does not constitute a threat to national security or to the operations of the Polish armed forces," Mariusz Blaszczak said in a statement.

The minister said the leaked database "only contains information that is (already) available to the public. It can be accessed, for example, through public procurement procedures that are conducted and published openly".

The military police were leading an inquiry "into the civil servant who put the information on an unauthorised server, without being authorised to do so", he added.

Blaszczak's statement came just hours after Polish website Onet.pl said a database containing the equipment requirements of every single unit in the army had been leaked online.

The Polish opposition has demanded Blaszczak's resignation and called for a security check of the defence ministry.

Onet.pl said each of the 1.75 million entries in the database detailed the equipment needs of an army unit.

These ranged from F-16 fighter jets, heavy weapons, spare parts, munitions and IT equipment to uniforms, underclothes, blankets, flags and even diplomas.

The database provides a precise snapshot of the state of the army's equipment at any one time, indicates whether this equipment is in working order and what elements are lacking.

It also gives details of the type of software the military uses and the licences it possesses.

A section of the database lists weapons and machines the Polish armed forces have bought from third countries.

Onet.pl said the leaked information had already been downloaded by internet users from more than a dozen countries, including Russia and China.