Here are the 20 seats where the Brexit Party performed strongest and hampered Tory chances of winning:
Barnsley Central: Labour 14,804 votes, Brexit Party 11,233 votes, Tories 7,892 votes. Labour majority: 3,571
Barnsley East: Labour 14,329 votes, Brexit Party 11,112 votes, Tories 10,377 votes. Labour majority: 3,217
Kingston Upon Hull East: Labour 12,713 votes, Tories 11,474 votes, Brexit Party 5,764. Labour majority: 1,239
Hartlepool: Labour 15,464 votes, Tories 11,869 votes, Brexit Party 10,603 votes. Labour majority: 3,595
Doncaster North: Labour 15,740 votes, Tories 13,370 votes, Brexit Party 8,294 votes. Labour majority: 2,370
Easington: Labour 15,723 votes, Tories 9,142, Brexit Party 6,744 votes. Labour majority: 6,581
Wigan: Labour 21,042 votes, Tories 14,314 votes, Brexit Party 5,959 votes. Labour majority: 6,728
South Shields: Labour 17,273 votes, Tories 7,688 votes, Brexit Party 6,446 votes. Labour majority: 9,585
Kingston Upon Hull West: Labour 13,384 votes, Tories 10,528 votes, Brexit Party 5,638 votes. Labour majority: 2,856
Washington and Sunderland West: Labour 15,941 votes, Tories 12,218 votes, Brexit Party 5,439 votes. Labour majority: 3,723
Normanton: Labour 18,297 votes, Tories 17,021 votes, Brexit Party 8,032. Labour majority: 1,276
Blaenau Gwent: Labour 14,862 votes, Brexit Party 6,215 votes, Tories 5,749 votes. Labour majority: 8,647
Rotherham: Labour 14,736 votes, Tories 11,615 votes, Brexit Party 6,125 votes. Labour majority: 3,121
Wentworth and Dearne: Labour 16,742 votes, Tories 14,577 votes, Brexit Party 7,019 votes. Labour majority: 2,165
Jarrow: Labour 18,363 votes, Tories 11,243 votes, Brexit Party 4,122 votes. Labour majority: 7,120
Doncaster Central: Labour 16,638 votes, Tories 14,360 votes, Brexit Party 6,842. Labour majority: 2,278
Cynon Valley: Labour 15,533 votes, Tories 6,711 votes, Brexit Party 3,045 votes. Labour majority: 8,822
Makerfield: Labour 19,954 votes, Tories 15,214 votes, Brexit Party 5,817 votes. Labour majority: 4,740
Rhondda: Labour 16,115 votes, Tories 4,675 votes, Brexit Party 3,733. Labour majority: 11,440
Kingston Upon Hull North: Labour 17,033 votes, Tories 9,440 votes, Brexit Party 4,771 votes. Labour majority: 7,593