Vermont's largest health insurer is asking state regulators to approve an average 9.8 percent increase in premiums for plans it offers through the state's federally mandated exchange.

Blue Cross Blue Shield of Vermont said Monday the increase is needed to cover rising medical and pharmaceutical costs for their members and increased federal fees charged to insurers as part of the Affordable Care Act.

If the Green Mountain Care Board, which is responsible for reviewing and approving the exchange rates, signs off on Blue Cross' request, monthly premiums for the six standard plans it offers on Vermont Health Connect would go up between $20 and $70 in 2015.

In last year's rate review process Blue Cross' requests for exchange plan prices were revised down an average of 4.2 percent by the board.

MVP Health Care, the other insurer offering coverage through the exchange, did not provide its rate request filings or return calls for comment by publication time Monday. The filings are public record and had to be submitted to the Green Mountain Care Board by Monday. The filings for both companies will be posted on the board's website Tuesday, said Susan Barrett, the board's executive director.

According to a breakdown of the rate request provided by Blue Cross, almost 5 percent of the overall 9.8 percent increase is to cover federal charges associated with the Affordable Care Act.

Payments to providers are expected to increase 4.8 percent in 2015, according to Blue Cross. That increase is regulated, in part, by the state because the Green Mountain Care Board must approve hospital budgets.

Another 1.3 percent of the requested increase is to cover additional child dental services required by the state and to keep other costs associated with a health plan from rising. The out-of-pocket costs, such as co-pays, coinsurance and deductibles associated with exchange plans will not go up, said Kevin Goddard, vice president of external relations for Blue Cross.

The Green Mountain Care Board has 90 days to review, possibly adjust and then approve the rate requests of the two carriers. The new rates will take effect in January.