Nicklas Bendtner has criticised Arsenal for relegating him to the reserves and letting him train on his own before his sudden return to the first team in September, and also said that he is "training more seriously than ever" in order to find himself a new club.

The Danish striker, the club's only back-up to Olivier Giroud, has told the Danish paper Berlingske in an exclusive interview that he was "very disappointed" when Arsène Wenger phoned him on transfer deadline day to tell him that he would be staying at the club. "Everything was in place for me, there were three clubs that were just waiting for me to say 'yes please' to them," he said. "I was very disappointed when he [Wenger] phoned because I was ready to move on. I didn't actually think that they wished to keep me."

The phone call came on 31 August and the day after he returned to train with the first team for the first time in two years. The 25-year-old Dane spent last season on loan at Juventus but played only nine games after suffering an injury. "As I have been at the club since I was 16 I found it ridiculous that they placed me in the reserves and let me train on my own. [But] suddenly everything was like old times again. I was training with the first team, I was hanging out with the first team and I had a dietician again. From being completely out to being completely in again."

The comments are unlikely to go down well with Wenger, especially on the eve of the club's biggest game of the season and the fact that the manager has no one else to turn to in the strikers' department. The interview was conducted the day after Bendtner had started for Arsenal against Chelsea in the Capital One Cup on 29 October but published online in Denmark on Saturday night, less than 24 hours before the game at Old Trafford.

The striker clearly feels that he still wants to leave the club despite being back in Wenger's thoughts and his latest comments may hasten his departure. "I have to fight twice as hard during every game and also score to have a chance to start next time, which in itself is hard when I haven't hardly played in a year due to injury and have not had a pre-season together with the others on the team," he said.

Bendtner was booed by a section of Arsenal fans during the 66 minutes he played against Chelsea before being replaced by Giroud, and he has been targeted on social media as well, but says that it does not affect him "one bit".

He said: "That's just what it is like to be a footballer. But I will remain strong because if I start to listen or believe in them I could quickly find myself in a black hole."

The striker has been criticised in Denmark as well, where a serious of controversies have overshadowed his performances for the national team, but he showed everyone that he can score against the best teams in the world with his two headed goals when Denmark drew 2-2 with Italy in a World Cup qualifier last month.

Typically for Bendtner, who has not had much luck the past few years, Italy equalised in added time, through the former Liverpool player Alberto Aquilani, which ruined not only his night but ended his and Denmark's hopes of playing in next year's World Cup finals.

"At the moment I am an easy target for [some of the fans] because I want to leave the club and Arsenal don't want to keep me.

"And these haters – they always choose the same solution. But I think it is unfair to have a go at me when I had a transfer in place in the summer and Wenger told me to stay.

"I am training far more seriously [now] than I have ever done in Arsenal. I am in the process of building myself up so that I become this strong machine, this perfect product to sell. I want to start as strongly as possibly in my next club."