People must be able to have "confidence" in their politicians, Theresa May has said in response to the allegations surrounding Keith Vaz.
The Prime Minister said MPs have a duty to their constituents but stressed that decisions on his future were a matter for Mr Vaz.
Theresa May has said that "Brexit means Brexit" in her first major speech since launching her leadership bid.
Speaking in Birmingham, the Home Secretary said: "Our country needs strong, proven leadership to steer us through this time of economic and political uncertainty and to negotiate the best deal for Britain as we leave the EU and forge a new role for ourselves in the world - because Brexit means Brexit and we're going to make a success of it."
The Home Secretary, Theresa May, will visit Telford-based firm SmartWater today.
Along with the Conservative candidate for Telford, Lucy Allan, she will tour the company's base at Nedge Hill Technology Park to see how the local firm has grown to become an international success.
SmartWater uses forensic technology to form a security mark on items which are all but invisible to the naked eye.
Each batch is unique, like a fingerprint, meaning stolen goods can quickly be identified and returned to their rightful owner.
It also transfers onto hands and clothes, meaning anyone who has handled the goods will also be marked.
Equalities minister Lynne Featherstone has told Daybreak that forced marriage is "totally unacceptable", as plans are announced to make it a criminal offence.
Meanwhile, the Home Secretary Theresa May has said the Government's concern "will always be for victims".