Mr Williams said, "16 and 17 year olds are more than capable of engaging in political debate. Young people are deemed responsible enough to pay taxes, to get married, to fight and possibly die for their country, but yet they are not deemed responsible enough to choose a government".
Mr Williams spoke to a full chamber, losing the division by just 8. 128 MPs voted for the change with 136 voting against.
Read the full text of Stephen's speech by clicking on the speeches link on the left hand side.