The embattled drug developer has set a date of 9 March for the extraordinary meeting requested by the dissidents after delaying the shareholder circular for two days to give them time to back down.
The board is urging investors to vote against the appointment of Bob Thian, the chairman of the filtration-paper company Whatman, as a director. The rebels plan to install him as an executive chairman.
The dissidents ousted the founder and previous chairman of SkyePharma, Ian Gowrie-Smith. But the company then snubbed them by appointing Mr Karabelas, who has sat on the board for five years as non-executive chairman.
Mr Karabelas said yesterday: "I don't know how an executive chairman who has made a deal with the minority shareholders is going to work in the interest of all shareholders. It's an attempt to hijack the company under the guise of, 'We are the owners of the company'. He added: "These are attempts to take over the company without a premium."
The dissident group comprises North Atlantic Value (NAV), part of JO Hambro, Morley and Insight, and represents 14.2 per cent of SkyePharma shares. NAV was behind Mr Thian's appointment to Whatman. He is credited with making big improvements there, although a recent profits warning cast doubt on his achievements and Whatman has had three chief executives in two years.
Mr Karabelas claimed Mr Thian was the rebel group's second-choice candidate, saying: "Here's a chairman who has difficulty keeping CEOs. In baseball it's three strikes and you're out."
NAV stressed the credentials of Mr Thian and argued: "Many of the executive management team associated with SkyePharma's dismal track record continue to be members of the board.... It is imperative that a totally independent chairman is appointed immediately to give shareholders confidence that these serious issues will be addressed as soon as possible."
SkyePharma's future hinges on HBM Bioventures, the Swiss venture-capital group headed by the former Roche finance director Henri Meier. It is the single largest shareholder in SkyePharma, with a 9.3 per cent stake. Mr Karabelas flew to Switzerland last Friday accompanied by his new chief executive, Frank Condella. Mr Karabelas was quietly confident HBM would back the board, saying: "It was a very successful meeting." NAV has also been to Switzerland to try to win HBM's support.
Mr Karabelas admitted: "Clearly there is disappointment about what's happened to the share price. That's something I'm very sympathetic to."