Everton have conceded five goals in their last two matches.
The Toffees have conceded five goals in their last two games, against Manchester United and Arsenal, and Barkley have been left frustrated with the porous nature of his side's defence.
Everton have generally been well organised this season, but they have started to give away cheap goals, and Barkley insists that they cannot continue to be so weak defensively if they are to meet their aims this season.
“As a squad we don’t concede too many of those goals, but have done in the last two games," he said.
“So we’ve just got to go back to training and try and perfect that part of our game and try and get it right.”
Everton were outplayed by Manchester United, but against Arsenal the Merseyside outfit could feel aggrieved not to have collected at least a point.
Roberto Martinez's side matched the Gunners for large parts of the match, and they created a host of chances, but they were let down by a terrible spell in the first-half.
Arsenal scored two goals in quick succession to race into a 2-0 lead, and although Barkley pulled one goal back, they couldn't net an equaliser.
That defeat leaves the Toffees down in 11th place in the Premier League table, with their next league match coming against Sunderland.