In 1998 he was elected into the lower house of parliament for the PvdA as finance specialist. He campaigned together with Rick van der Ploeg and Willem Vermeend as "the Polderboys" and gave lectures in economics at universities. In 2000, due to a cabinet reshuffle, he succeeded Willem Vermeend as staatssecretaris for Finance, and became responsible for taxation, monetary policy and finances of lower-level government. Together with Finance Minister Gerrit Zalm he was able to get parliamentary support for a radical reform of the tax system. After the May 2002 elections he returned to parliament, as a specialist on income policy and health affairs.