The state’s top health insurers are filing a lawsuit contesting a decision by state regulators to reject the vast majority of small business premium increases they sought this year.

Insurance Commissioner Joseph Murphy said last week he rejected 235 of 274 proposed rate increases because they included "excessive increases and rates unreasonable relative to the benefits provided."

The insurers said Murphy’s decision will end up creating greater costs and more confusion in the marketplace.

Eric Linzer, spokesman for the Massachusetts Association of Health Plans, called the state’s effort to artificially cap rates "a reckless decision that is based in politics and will wreak havoc on the entire health care system."

Linzer said the move could also undermine the state’s landmark 2006 health care law.