The recent rapid rise in prices has started to affect consumers' purchasing behaviour, according to OP Financial Group's bank card payment data.

Inflation has accelerated to its highest level in decades, a situation the financial institution said was causing consumers to buy less food and fuel this summer compared to last year.

However, OP noted in a statement issued on Thursday that the decline was a gradual one, not a sharp change.

It noted that Finland's inflation rate rose to around 7.8 percent last month, the highest rate the country has seen since 1984. OP mostly attributed the spike in fuel and food prices to Russia's invasion of Ukraine.

The financial group said that energy prices are up 40 percent and fuel costs have ballooned by nearly 60 percent since last year. Meanwhile, food prices cost almost 11 percent more this year.

"The reduction in energy and food supplies has increased the prices of those products and decreased their consumption. The consumption decrease is clearly seen in card payment data, as purchase volumes of fuel and food, for example, are now well below levels seen last year," said Tomi Kortela, OP's senior economist.

Rising fuel prices have prompted a 10 percent decline, year on year, while consumption of foods is about five percent lower than last summer, using constant pricing estimates, OP said.

It noted that it is likely that consumers are not yet buying less food than before but rather choosing more affordable products.

Kortela said he thinks consumers reducing purchases of pricier products was a step in the right direction.

"You have to try to adapt your finances to the changed environment. Of course, households have very different possibilities to adjust consumption, so inflation can test different households in different ways," he said.

However, the overall increase in prices is still "clearly greater" than consumers' purchase volumes, so much more money is being spent on fuel and food than last year, according to the bank.

The bank forecast Finland's economic growth will slow down to just 0.6 percent next year, from this year's anticipated growth rate of 2.0 percent.