Herfkens, a former Labour party aid minister worked as a special advisor to secretary general Kofi Annan on poverty issues between 2002 and 2006.
The MPs insistence that the money be returned comes as a UN report on the affair appears to hold the Dutch government and the UN itself partly responsible.
The report, different versions of which are carried by both the NRC and the Volkskrant newspaper, says that Herfkens ‘ appears to have unknowingly breached the staff regulations, in good faith and without mal-intent’.
Herfkens was given and signed for a copy of the staff regulations during her induction period. She told the NRC earlier this year she was too busy to read them.
Foreign minister Maxime Verhagen said earlier that he would try to recoup the money if legally possible and if it was shown that Herfkens knew she was breaking UN rules.