June 23 (Reuters) - The European Union formally requested in a letter on Wednesday that the world's largest economies explore the introduction of a global tax on financial transactions.

Writing to the G20 before a summit in Toronto on June 26-27, Herman Van Rompuy, the president of the EU Council which represents EU member states, said the world needed a level playing field on bank levies and transaction taxes.

We consider that international work on levies and taxes on financial institutions should continue to maintain a worldwide level playing field, he said in the letter, written jointly with European Commission President Jose Manuel Barroso..

Also the introduction of a global financial transaction tax should be explored and developed further in that context.