The vote comes as David Cameron hosts an anti-corruption summit in London, with the government claiming to have "led the way on tackling tax evasion and tax avoidance", and established a public registry of company beneficial ownership information and "pushed its G7 and G20 partners to do the same".
However, five times in the past 13 months, Conservative MEPs have voted against measures to tackle tax dodging, from public country-by-country reporting of tax affairs to a common list of tax havens to the shareholders rights directive to a clampdown on tax fraud, including aggressive tax planning.
Neena Gill MEP, member of the European Parliament special committee on tax, added:
"The Conservatives have been all talk when it comes to tackling tax avoidance - we've had pledges from the top of the Tory Party, and tough talk - but in the European Parliament, when they think no one's looking, the Tories have voted against action.
"Do the Tories believe in the public and transparent mandatory automatic exchange of country-by-country reports between EU countries, or not? Do they believe information exchanged between various tax authorities should be publicly available?
"Tomorrow, Tory MEPs have an opportunity to vote for EU action against tax avoidance - will they take it?"