Kettering Council made more than £250,000 from parking charges in the past financial year.
But that amount is down by 28.5 per cent since 2010/11, according to the latest figures.
Research carried out by the RAC Foundation show Kettering made a profit of £291,000 in 2014/15, down from £407,000 four years ago.
The authority’s revenue has been on a steady decline with only 2013/14 showing an increase, when it rose from £341,000 to £354,000.
Corby’s car parking revenue has fluctuated but has increased from £45,000 in 2010/11 to £113,000 in 2014/15.
It made a loss of £5,000 in 2011/2012 before hitting a high of £146,000 in 2013/14.
Wellingborough and East Northants continue to subsidise their car parks to enable people to use them for free.
This decision cost Wellingborough Council £343,000 in 2014/15, and East Northants Council £74,000, in both cases £3,000 more than three years ago.
East Midlands UKIP MEP Margot Parker believes town shoppers should be able to park for free for 30 minutes.
She said: “I am keen on helping to protect town centre stores and keeping our shopping streets vibrant with a range of different shops and traders.
“We in UKIP want to provide more free parking in our towns and it was our idea to introduce free parking for the first 30 minutes of a stay.
“Local authorities should not target the motorist – always an easy hit – to fill holes in budgets.
“They should be protecting and nurturing small businesses and traders – providing as much free parking as possible is one way of doing that.”
To view the figures in full click here.