A third of trades on Europe's traditional stock exchanges are not being completed at the best price available, according to a study by pan-European equity trading platform Equiduct.

Through an analysis of data from the platform, Equiduct showed that of the 97 billion euros in trades completed during January, 33.4 percent of the trades, across 500 of the largest European stocks, could have achieved a better price on a different venue.

"Had the best price been achieved in the month of January on our sample of around 500 leading European stocks, buyers would have been able to save 30 million euros on the prices actually paid," said Artur Fischer, joint CEO of Equiduct.

Equiduct, majority owned by Boerse Berlin, is compiling data to help users to cross-check execution quality and gain greater clarity on the performance of banks and brokers. It operates a rival trading platform to the big exchanges.

Should market share be allocated by the availability of best prices, 13.4 percent of pan-European market share would migrate from the incumbent exchanges towards the new multilateral trading facilities (MTFs) such as BATS, Chi-X, Turquoise and Nasdaq OMX, the study showed.

Among the incumbent exchanges, the London Stock Exchange is leading the way to catch up with the upstarts in its efforts to achieve a better price, Fischer said.

According to its study, about 28 percent of trades on Euronext, the Europe arm of transatlantic exchange group NYSE Euronext , in January were not executed at the best price.

Some 25.7 percent of the LSE trades and 31.1 percent of trades on Deutsche Boerse's equity platform Xetra were not done at the best price.

Xetra would have seen its market share drop to 15.6 percent from 20.1 percent if all trades had been executed at the best price available.

Euronext's market share would have decreased by 5.2 percentage points to 22.5 percent and the LSE's share would have been trimmed by 3.9 percentage points to 25.9 percent