Middlesbrough manager Aitor Karanka has criticised the club's lack of activity in the January transfer window and said they are being left behind rivals in the battle to avoid the Premier League drop.

Middlesbrough, who are four points and two places above the relegation zone, host West Bromwich Albion later on Tuesday aiming to end a winless run in the league that stretches back to mid-December.

The club signed Rudy Gestede from second-tier Aston Villa and Patrick Bamford from Chelsea this month, but neither forward has played much this season.

"We need to improve the team, and the club knew a month and a half ago the players that I wanted," the Spaniard told members of the media.

"I always said the aim in the transfer window was to improve the squad. At the moment, we haven't done that. We will be disappointed if nobody else comes in, but I have tried my best.

"Teams in our position are signing players for £14m – we are signing players that didn't play in the Championship."

Karanka said it was unrealistic to expect Bamford, who made six substitute appearances while on loan at Burnley prior to joining the club, to shoulder the scoring burden.

"If we are expecting that Patrick was going to arrive and score five goals straight away then we are making a big mistake because he is not ready now," he added.

Karanka does not want to burden new signing Patrick Bamford with the task of keeping Boro in the Premier League (Getty)

"I don't know why we haven't signed our targets. That is not my job. I am the coach," added Karanka, who earlier this month hit out at the club's fans for creating an "awful" atmosphere in a game against West Ham.

"When we got promotion last season, there were a lot of people who got a medal. A lot of people had a medal, and a lot of people had done their job. Now? I don't know... With this group of players, the only thing I can do is trust and believe."