Republican candidates in critical battleground races in the US midterm elections are seizing on soaring mortgage rates to attack Democrats on inflation, as they hope that a renewed focus on the economy will help them win control of Congress in November.

High petrol prices have continued to serve as the Republicans’ main weapon on the campaign trail despite an overall decline in recent months. But the Federal Reserve’s steep interest rate increases this year have given them additional ammunition by triggering a swift rise in mortgage rates to levels not seen since the 2008 housing-led financial crisis.

According to the most recent data, the average interest rate for a 30-year fixed-rate mortgage in the US has risen to about 6.7 per cent, doubling from about 3 per cent in January.