Curbishley was under pressure to succeed and produce attractive football
Alan Curbishley has been accused of contributing to his own downfall at West Ham after making costly mistakes in the transfer market.
Curbishley resigned as the club's manager, complaining transfer policy had been taken out of his control.
But agent Kia Joorabchian, a transfer adviser at Upton Park, said Curbishley had made life difficult for himself.
"The board left it in the hands of someone they assumed was capable, things went wrong," he told BBC Sport.
Curbishley was particularly annoyed by the sale of George McCartney and Anton Ferdinand before the close of the transfer window and said it had amounted to "a breach of trust and confidence" giving him "no option but to leave".
Ferdinand and McCartney were sold to Sunderland for about £8m and £6m respectively but Joorabchian described the fees as "tough numbers to reject".
Joorabchian, who helped West Ham sign Argentine duo Carlos Tevez and Javier Mascherano in 2006, said the club had to trim the wage bill and sell players before bringing in new recruits.
Curbishley, who spent 15 years in charge of Charlton before joining the Hammers, signed the likes of Freddie Ljungberg, Kieron Dyer and Craig Bellamy but injuries meant the trio featured only sporadically.
Ljungberg joined the Hammers for a fee approaching £3m but received a significant sum to end his contract after only one year of a lucrative four-year deal.
Joorabchian said Curbishley and former chairman Eggert Magnusson were both culpable.
"I think from the day Curbishley entered the club, he made most of the decisions with regard to the incomings of Luis Boa Morte, Nigel Quashie, Dyer and Ljungberg," added Joorabchian.
"I wasn't deeply involved at that time but it was pretty clear cut that he was very much involved in those.
Joorabchian advises the West Ham board on transfers
"I think the board realised that there were a lot of mistakes made during that period when Mr Magnusson was in charge.
"Not to put blame on either of them but the salaries that were being given and the players that were being brought in were probably not the board's idea of taking the club forward."
Towards the end of last season West Ham had a wage bill approaching £50m a year, which left the board, according to Joorabchian, with a "difficult task" to buy new players.
"Your wage structure has to be able to cope with the players coming in and if you have a lot of players on your books with high salaries, who are probably not very productive on a day-to-day basis," he stated.
I can assure our loyal supporters that we are working hard to bring sustained success to West Ham United
West Ham chairman Bjorgolfur Gudmundsson
"Your first stage is to release some of that wage structure to get into the transfer market again.
"I think it's very sad what happened to West Ham in the last year, with the players and the direction which they went.
"I do feel for Curbishley because he's a manager who has resigned under pressure but, unfortunately, the game has become so competitive that I think every manager understands that there are three major issues.
"You have to succeed in the transfer window; you have to make sure you have a winning side; and - when you're at a club like West Ham - you have to play good football."
Curbishley's exit leaves West Ham searching for their fifth manager in seven years, with Croatia coach Slaven Bilic, Portsmouth manager Harry Redknapp and former Hammers forward Paolo Di Canio all linked with the role.
However, despite the recent upheaval at the club, chairman Bjorgolfur Gudmundsson maintains there are positive times ahead.
"In my first full season as chairman of this great football club, I can assure our loyal supporters that we are working hard to bring sustained success to West Ham United," he insisted
"Everyone, including the chief executive and board, is committed to this common goal.
"We have a long-term strategy that takes into account all aspects of West Ham United's past, present and future and we will not be deterred.
"Our fans can look forward to many positive years on and off the pitch."
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