Montgomery County residents should be willing to pay some of the increase in utility bills that may result if a proposed increase in the Prince George's County business property tax is approved in the Maryland General Assembly, Prince George's chief legislative lobbyist said today.

"We just want everyone to be treated equally," Royal Hart said after an unexpected appearance before the Montgomery House delegation to make a pitch for his county's efforts to get the tax passed. Prince George's taxes on utilities "have been lower than Montgomery's for the last few years, but we have not been getting a lower rate than Montgomery."

Hart appeared after being notified that the Montgomery legislators had just requested that an amendment be written for the tax proposal, which would increase personal property taxes assessed against utilities and other businesses in Prince George's for two years.

Utility companies have warned that should the bill pass, they will pass on to consumers the additional costs--more than $7 million a year, according to Prince George's officials. The Montgomery amendment would prohibit utilities from passing the costs on to Montgomery users.

"We should not put our constituents in the position of having to pay through their gas bill for problems in Prince George's," said Del. Idamae Garrott. The delegation is scheduled to vote on the amendment Monday night.

The utilities' cost of doing business, Hart argued, has been cheaper since Prince George's voters passed a property tax cap in 1978, and therefore utility rates for residents in both Montgomery and Prince George's have been lower than they otherwise would have been. Residents of Prince George's and Montgomery counties now pay the same rate for their utilities.

PEPCO officials estimate that their company has saved about $8 million since the Prince George's cap went into effect in 1979. Utility bills have continued to rise since then, but PEPCO officials say the increase has not been as high as it would have been without the tax relief.

If the proposed tax increase is passed, county officials estimate that PEPCO will be levied an additional $5.4 million a year, about $6.50 for users in the two jurisdictions. Without any help from Montgomery, Prince George's officials say their residents will have about $13 added to their gas bills.

The tax measure is one of two proposed by Prince George's County Executive Parris N. Glendening to offset a projected fiscal 1984 deficit of $30 million, which county officials primarily blame on the 1978 tax cap.