Four months after its last rate increase in Maryland, Chesapeake and Potomac Telephone Co. yesterday proposed a new boost in phone bills for intrastate services.

The latest request is for an across-the-board increase of 2.47 per cent, which will raise basic monthly charges for Maryland customers by 25 to 30 cents and give the company $11.4 million a year in added revenues.

In May, the Maryland Public Service Commission gave C&P a $19.1 million rate increase package that added about 25 cents to basic bills and boosted pay phone calls to 15 cents.

The additional $11.4 million is needed to pay raises provided in a new three-year contract with the Communications Workers of America, which was signed in August, a C&P spokesman said.

He said the company knew when it got the May increase that another request would be made later in the year to cover the wage pact. C&P asked the Public Service Commission at that time to approve a larger increase in anticipation of higher wage costs, but was turned down.

The PSC has 90 days to act on the newest rate increase.

C&P said the across-the-board boost in phone bills is required to comply with a recently passed Maryland law requiring any additional revenues be raised equally from all customers.

No increases in message unit charges or coin telephone rates are included in the latest rate increase request.

The new rates would enable Maryland C&P to earn the 9.25 per cent annual rate of return on invested capital approved by the PSC in May.

The new rates asked in Maryland compare with basic rates of $10.80 per month in Northern Virginia and $9.99 per month in the District of Columbia, though phone services vary from community to community.