Can a lawyer be sued for deliberately prolonging a case for his own financial gain?

Nope. Not only us this a daily occurrence, but the lawyer for the other side owes you no duty. I am going to post this under ethics.

A lawyer's job is to ethically do whatever possible for his or her client. If delaying a case weakens the opposing side without violating a law or professional code of ethics, its a valid tactic. No matter ancillary consequences.

One can be sued for almost anything, but suing a lawyer (successfully) for "prolonging" a case will be extremely difficult. I doubt you will prevail.

If these facts are against or alleged against the other party and their counsel, then that is really between them and arguably what opposing counsel and ongoing litigation seems designed to do (from adverse party view point). I feel your frustration. If your facts are geared to your claim and your own attorney, that is another matter entirely. Deliberately prolonging a case for his own financial gain at the expense of own client (if supported and documented) is a conflict to be examined. CA Rule of Professional Conduct (generally, though not exactly applicable on fact presented) Rule 3-300 states: Avoiding Interests Adverse to a Client - A member shall not enter into a business transaction with a client; or knowingly acquire an ownership, possessory, security, or other pecuniary interest adverse to a client, unless each of the following requirements has been satisfied: (A) The transaction or acquisition and its terms are fair and reasonable to the client and are fully disclosed and transmitted in writing to the client in a manner which should reasonably have been understood by the client; and (B) The client is advised in writing that the client may seek the advice of an independent lawyer of the client's choice and is given a reasonable opportunity to seek that advice; and (C) The client thereafter consents in writing to the terms of the transaction or the terms of the acquisition. CA Rule Rule 3-500 regarding Communication states: A member shall keep a client reasonably informed about significant developments relating to the employment or representation, including promptly complying with reasonable requests for information and copies of significant documents when necessary to keep the client so informed. Further, CA Rule 3-510 Communication of Settlement Offer states: (A) A member shall promptly communicate to the member's client: (1) All terms and conditions of any offer made to the client in a criminal matter; and (2) All amounts, terms, and conditions of any written offer of settlement made to the client in all other matters. If you have issues and concerns with your own attorney, document them in writing and request written response from attorney if you have not already done so. Then you will have more information on how and if to proceed against your attorney either through local counsel in jurisdiction and/or jurisdictional bar association.

No but if this is a case where the lawyer on your opposing side engages in these tactics, sanctions are available for causing unnecessary delays in resolving the matter. You need an attorney to help you.