British finance minister George Osborne's market sensitive statement to parliament on the budget was leaked on the internet minutes before his speech started.

A copy of what appeared to be the front page of the London Evening Standard, with full details of economic forecasts and changes to taxes, appeared on the blog of political commentator Guido Fawkes at least fifteen minutes ahead of Osborne's speech on Wednesday.

The newspaper's political editor Joe Murphy apologized for the "very serious mistake" in a tweet, as copies of the paper's front page were seen being circulated in the House of Commons as Osborne spoke.

The leak comes at a sensitive time between press and political relations in Britain, with a new system intended to regulate the country's scandal-hungry press agreed on Monday.

(Reporting by Rosalba O'Brien, editing by Guy Faulconbridge and Jeremy Gaunt)