The Labour leader, Ed Miliband, has welcomed new the Middlesbrough MP to the Commons.
Andy McDonald MP had a majority of more than 8,000 in Thursday's by-election over UKIP who came second for the first time in a parliamentary seat in the region.
Mr Miliband praised Mr McDonald for his services to Middlesbrough over the years.
He said: "You are somebody who served the people of Middlesbrough as a solicitor. You worked incredibly hard for people there."