Stephen Timms, the member of Parliament for the constituency of East Ham and the former financial secretary to the Treasury, was being treated at the Royal London Hospital after the attack, a statement from the Labour Party said.
Timms, 54, was taken to the Royal London Hospital with injuries that are not believed to be life-threatening. "He has received visitors and is in good spirits," the statement said.
Unmesh Desai, who acted as Timms' aide during Britain's recent general election, said the lawmaker would be kept in the hospital overnight for observation and treatment. He said Timms was "obviously shaken."
The lawmaker was holding his regular consultation with constituents when a woman - who neither Timms nor his staff recognized - approached him, Desai said.
A spokesman for London's Metropolitan Police said a 21-year-old woman was arrested in connection with the incident.
Timms has represented the area since 1994. He was re-elected last week with the largest majority in Britain's House of Commons, Desai said.