The acting speaker of the lower house of Brazil's Congress has annulled last month's vote on impeachment, delaying the process against embattled President Dilma Rousseff.

A Senate vote on whether to accept the impeachment process had been scheduled for Wednesday. But Monday's request by Waldir Maranhao means the matter goes back to the Chamber of Deputies.

The reasoning for the decision was unclear.

The decision is a huge victory for Rousseff, who faced suspension from office had the Senate taken up the matter and ruled against her.