MADRID (Reuters) - Spain's Prime Minister Mariano Rajoy on Wednesday said he would soon propose new bills to regulate more strictly the financial activity of political parties and crack down on corruption.

Speaking before the parliament on the occasion of his annual speech on the state of the nation, he also said he would propose a reform of criminal law to enforce tougher sanctions against cases of corruption among senior political officials.

The ruling People's Party has been buffeted since January by media reports alleging its former treasurers operated a slush fund with donations from construction industry executives that were then doled out to Rajoy and other party leaders.

(Reporting by Emma Pinedo and Julien Toyer; Editing by Clare Kane)