Ace International's Gibraltar office is understood to be the sole underwriter of the Gibraltar government's insurance cover.
Ace Gibraltar Ltd, which was established in 2001, underwrites the government's insurance needs including medical malpractice, property, motor, and professional indemnity.
It is also understood that government staff are offered a discount for home and contents and motor policies.
An Ace spokesman said: "Ace saw an opportunity in the local market and has been participating for three years.
"We write commercial property and casualty packages and have a small portfolio of household insurance. The total value of this book is less than £5m.
"Ace has a significant participation in the insurances of the Gibraltar government, but it is not our policy to comment on individual client portfolios."