The retired general was banned from doing any military consulting work until the end of this January under a contract with the ministry, which found last week that he registered a consultancy before it expired.
"Lindberg has infringed on the contractual terms of the quarantine agreement. The Defenсe Ministry sees the breach of the contract as serious and condemns Lindberg's failure to disclose it", the press release read.
He will not be fined because the company did not start working with the US aerospace giant — which sought to sell $10.8 billion worth of fighter jets to Finland — until after the end of the cooling-off period, the ministry added.
Lindberg left the post of the commander-in-chief at the end of July 2019 after his contract had expired.
According to the STT news agency, the US manufacturer informed the Finnish Defence Ministry about receiving Lindberg's consultations on Wednesday.
Lockheed Martin was invited by the Finnish government to compete for the supply of fighter jets on an equal basis with four other manufacturers.
The Finnish Defense Ministry intends to purchase about 64 new fighter jets worth 10 billion euros.