Angela Smith MP has moved to the Liberal Democrats after three months of sitting as an independent MP
The MP for Penistone and Stocksbridge joined the Liberal Democrats due to extremist grips on both Labour and the Conservative parties.
Ms Smith is the third MP to join the Liberal Democrats in a week, bringing the total number in the House of Commons to 17.
In a blog post for the party published on Saturday, the MP called for more inclusive and tolerant politics as well as fighting against Brexit.
She wrote: "Our country deserves better than this. At a time of national crisis, people deserve a better choice than the two old parties.
"I am therefore delighted to be joining Jo Swinson and the Liberal Democrats.
"The Liberal Democrats are the strongest party to stop Brexit and build a society that gives opportunities to everyone, tackles the climate crisis and invests in our public."
She was welcomed by leader Jo Swinson, who had hinted in a tweet on Saturday afternoon that the anti-Brexit party would be gaining another member.
Ms Swinson wrote on Twitter on Saturday evening: "Welcome Angela Smith to the Lib Dems. She's the sixth new MP to join us in the last three months, along with over 30,000 new members. Together we can stop Brexit."
Ms Smith joins former Change UK members Chuka Umunna and Luciana Berger in joining the Liberal Democrats from the Change UK group which was formed in February.
She was one of 11 representatives who left Labour and the Conservatives to form the group, however she departed the group to sit as an independent MP in June.
Deputy Liberal Democrat leader Ed Davey also greeted Ms Smith to the party, tweeting: "We're going to need a bigger bench."