Prince George's County Executive Lawrence J. Hogan released a plan yesterday to increase county spending by $7.9 million this year. Almost all the increase, Hogan said, will go toward paying off a variety of debts the county has incurred.

The supplemental budget includes about $4.8 million needed to make up for the county's recent loss of borrowing power.

Prince George's can no longer issue bonds because its bonds must be backed up by an assurance of unlimited taxing power, which is no longer possible under the TRIM charter amendment limiting tax collections.

As a result, Hogan said in a statement issued with the supplemental budget, the county will be forced to pay debts on recently constructed hospital additions and other projects with operating funds.

The addition to the current $443 million county budget for 1979, which will have to be approved by the county council, also contains:

$1 million to make up operating losses in the county's hospital system.

$1.3 million to pay the county's share of Metro operating losses.

$765,000 for the Public Works and Transporation Department, to replace trucks and equipment that broke down during snow removal operations last winter.

Under Hogan's plan, most of the money for the new spending-or about $7.2 million-will come from the county's budget surplus for this year, which was created when costs fell short of what was planned in the original budget.

Hogan also cut $431,000 out of next year's budget for the new spending, but said that loss would be offset by an unexpected increase in state funds.

In a letter to the concil, Hogan warned that even the $7.9 million in new spending for this year may not be enough to make up some county debts, particularly those involving Prince George's General and Laurel hospitals.

In a statement released to the media, Hogan was careful to attribute to other politicians the blame for the new spending in ayear when citizens are cost-conscious.

Among other things, the press statement blamed the new spending on the county's state senators, who killed a bill in the state legislature that would have elminiated the conflict between TRIM and the county charter and allowed the county to borrow money through bonds.