BERLIN (Reuters) - German Finance Minister Wolfgang Schaeuble warned Britain on Monday against massive corporate tax cuts, saying that as long as the country remained a member of the European Union it must abide by the bloc's rules.

"Britain is still a member of the European Union," Schaeuble said when asked whether plans by Britain to cut corporate tax could trigger a dumping competition. "So they are bound by European law."

A spokeswoman for British Prime Minister Theresa May said on Monday the government had already outlined measures to cut corporation tax to 17 percent by 2020 and described any talk of further cuts as "speculative".

(Reporting by Gernot Heller; Writing by Joseph Nasr; Editing by Caroline Copley)