The pair joined Labour candidate Dr Paul Williams on the campaign trail in Hartlepool, paying a visit to Liberty Steel, just days before voters across town will head to the polls to elect their next MP.
The by-election in Hartlepool was triggered in March by the resignation of Mike Hill, who formerly held the seat.
Speaking to the Mail on Saturday, Sir Keir praised Dr Williams as a ‘loud and powerful’ voice for the town, and also commended his work on the front line of the coronavirus pandemic.
Local elections are taking place in England on Thursday, May 6.
Sir Keir and Ms Rayner also visited Durham on Saturday. Here are some pictures from their visit.