The Baggies went in front through Darren Fletcher's well-taken goal, before Chris Brunt profited from some slack Sunderland defending to brilliantly rifle in the second at The Hawthorns.

Swansea City's surprise win at Liverpool leaves Sunderland rooted to the bottom of the Premier League and manager Moyes was left despairing at his side's poor defending.

"We played better in the second than the first that is for sure. We are giving poor goals away and we are doing everything we can to eradicate it but it is a disease that we have got at the moment," he told BBC Sport.

"[The first goal] was well executed by Darren Fletcher. We defended the original corner well but the ball was bobbling around and we didn't clear it."

Moyes's defensive options have been depleted by Lamine Kone's absence due to his involvement with Ivory Coast at the Africa Cup of Nations, but the Scot is adamant that all is not lost in Sunderland's battle against the drop with 17th-place Swansea just three points above them.

"We are missing Lamine Kone at the back. He gives a steadying influence," he said. "This was always going to be a difficult period. We are making mistakes and I will take responsibility for that.

"We are not that far away [from safety]. We have to keep going and hope our turn for results will come. We have given away two or three poor goals but our play is not particularly bad but goals change games."

West Brom, meanwhile, is riding high in eighth after a third win in four league games.

Baggies manager Tony Pulis was full of praise for goal-scorers Fletcher and Brunt, while also hailing his side for buying into his style of football.

"First half we played really well. In the second you have to give credit to Sunderland they had more of the game than they did in the first half," Pulis said.

"We have done very well. The players have really embraced what we are trying to do and the atmosphere was fantastic again.

"Darren Fletcher's goal was fantastic and Chris has a wand of a left foot.  

"We are really pleased. We have a clean sheet in a game that was always going to be difficult game for us so we march on."