Paying politicians too much harms their work ethic, claims ground-breaking new research that could be used as an argument not to give British MPs a proposed 11% pay rise.

The findings, published in this month's issue of the Economic Journal, say that there is a significant link between how much politicians are paid and the effort they put into their day job. A study by Professors Naci Mocan and Duha Altindag examined changes to the salary structure of MEPs serving in the European parliament.

Before 2009, MEPs' salaries were determined by their home country, resulting in substantial national variations. A Polish MEP, for example, received €29,043, whereas their Italian counterpart was paid €142,512. However, in July 2009, MEPs' salaries were equalised, so that they were all paid €91,983. MEPs from Austria, Ireland and Italy experienced salary decreases, while all other MEPs had their salaries, which are fixed regardless of their attendance, increased.

The unique event allowed the economists to compare the effects of pay rises and decreases on MEPs' performances between July 2004 and December 2011. From this they drew a startling conclusion: MEPs who got an increase ended up attending fewer meetings, while those who had a pay cut raised their attendance rate. Each percentage increase in salary resulted in a decrease of around 0.04% in the number of days an MEP attended parliament. For example, the average French MEP, whose salary increased from about €76,000 to €92,000, ended up missing an additional parliamentary meeting a year.

"We find that a decrease in salaries motivates parliamentarians to increase their attendance," the economists write. The increase in salary also had a negative impact on the number of written or oral questions asked by parliamentarians.

"European parliamentarians are responsible for passing laws that govern the member countries," the two academics write. "They have control over the EU budget and they supervise the other EU institutions. So given the significance of the job, it might be presumed that the effort MEPs put into their work would not be influenced by their salary. The results of our analysis show that this is not the case."