Development of nearly 20 parks in Montgomery County, including the Little Seneca Regional Park, will be delayed over the next five years because of reductions in next year's park and planning budget.

The cuts were included in Montgomery's $29.9 million portion of the Maryland-National Capital Park and Planning Commission budget, approved by the County Council Saturday when it completed work on the county's 1983 operating budget.

Financial support of the commission, a bicounty agency, is split between Montgomery and Prince George's counties.

In Prince George's, which shares some of the administrative expenses of the agency, the County Council earlier approved a $29.8 million budget for park planning and development next year in that county.

The approved budget, which Montgomery Planning Board Chairman Norman L. Christeller called "barely tolerable," was more than $600,000 under the amount requested. Christeller had submitted a budget of $30.5 million, 11.1 percent more than last year. The County Council, following County Executive Charles W. Gilchrist's recommendation, pared the request down to the current figure after Gilchrist reminded members that other county agencies were asked to hold budget increases to 6 percent.

The final park and planning budget, which represents a 9 percent increase over last year's, nevertheless required the delay of some park development because of cost-of-living raises to employes and increased materials costs, Christeller said. Christeller also noted that without more funds, the commission will face more and more problems in trying to provide parks in the high-growth areas of the county on a par with other parts of Montgomery.