Brighton's Green Party Euro-MP Caroline Lucas has topped a table of UK MEPs doing most to champion European Parliament reforms and transparency - including full scrutiny of their expenses.
A new survey two weeks ahead of European Parliament elections puts Dr Lucas in joint first place.
Tory MEP David Sumberg (North West) is in bottom place under the rankings devised by Open Europe, the think tank campaigning for EU change.
The organisation awarded points to all 785 MEPs from 27 countries for their record over the five-year European Parliament term which has just ended.
Marks were given in 20 categories, from good attendance and fighting euro-budget waste to promoting accountability and ending expenses secrecy.
Open Europe monitored a range of MEPs' activities, including voting records, written declarations, and whether MEPs opposed "wasteful activities", such as meeting in Brussels and Strasbourg, and a controversial failed bid to get taxpayers to top up their pension contributions.
A Swedish Green MEP, Carl Schlyter, won the most points - 55 out of a possible 58.
The lowest score under the Open Europe formula was registered by Italian far-right MEP Roberto Fiore, who managed just two points, including a ten-point penalty for being convicted and jailed in Italy for alleged "subversive association" with terrorists.
Caroline Lucas scored 43 points, putting them in joint tenth place out of 785 MEPs and at the top of the UK table.
Mr Sumberg was given ten points, placing him last out of 78 UK MEPs and 729th out of all 785.
Open Europe said Mr Sumberg was absent from most of their "snapshot" votes, and in those that were recorded, Mr Sumberg voted to give more tobacco subsidies to farmers, and abstained on a European Parliament decision on whether or not to respect the outcome of the pending Irish referendum on the Lisbon Treaty.