Steve Clarke resigned as Chelsea’s assistant first-team coach yesterday evening to pave the way for a move to West Ham United, where he will work in a similar capacity under Gianfranco Zola, the new manager.

The former Scotland defender has agreed a three-year contract at Upton Park and his appointment will be announced in the next few days, once the club have agreed a severance package with Chelsea. The West London club are demanding £1.2 million in compensation because Clarke has two years left to run on his contract.

Clarke’s decision to sever ties with Chelsea that go back more than 20 years came as a shock to the club, with a series of meetings with Peter Kenyon, the chief executive, failing to bring a change of heart.

Luiz Felipe Scolari, the Chelsea manager, also attempted to persuade Clarke to stay, arguing that the Scot owed him a debt of loyalty after he allowed him to stay on this summer and claiming that his departure so soon after the start of the season would reflect badly on the club. But after four years as No 2 at Stamford Bridge, Clarke’s mind was made up.

He has been seeking a way out since José Mourinho left the club a year ago, despite the award of a new three-year contract in the light of the Portuguese’s departure. Clarke did not enjoy a close relationship with Avram Grant, Mourinho’s successor, although he was given wide-ranging responsibilities to take training by the Israeli, which shored up his position.

It is understood that Clarke has been effectively sidelined since Scolari was appointed in the summer, with the Brazilian relying almost entirely on Darlan Schneider, his other assistant, whom he brought with him from Portugal. Whereas Clarke was close to Mourinho and all his assistants, it is understood that he has not been invited into Scolari’s inner sanctum.

Although joining West Ham will be viewed as a backward step in some quarters, Clarke considers the opportunity to take charge of the coaching at a Barclays Premier League club as too good to refuse, as well as relishing the opportunity of linking up again with Zola, with whom he played for two years at Chelsea.

Clarke’s departure is a setback to Chelsea because he was very popular in the dressing-room, particularly with the English core of John Terry, Frank Lampard and Joe Cole. The club have no imminent plans to replace him.

While many West Ham fans will oppose the appointment of an individual with such close ties to their rivals, it will also go down badly with Chelsea supporters because Clarke was voted into their team of the century three years ago and was the last surviving link with the preRoman Abramovich era. The 45-year-old made 421 appearances for the club between 1987 and 1998, before returning as youth-team coach five years later.